AN2511 Application note
PMBusTM interface using ST7 I2C
Introduction
The PMBusTM (power management bus) is an open standard protocol that defines a means of communicating with power conversion and other devices. The PMBus protocol helps to establish the first truly open communications standard for the digital control of power systems. Implemented over the industry-standard SMBus (system management bus) serial interface, the PMBus protocol facilitates the programming, control and real-time monitoring of compliant power conversion products. This application note describes how to use the ST7 I2C peripheral for PMBus communication. The firmware of this application performs the PMBus bus protocols mentioned in PMBusTM power system management protocol specification v1.0. The device chosen here is ST72264G1 which has multi-master I2C capability. This microcontroller acts as the PMBus master. It controls the PMBus compatible slaves. The firmware described in this application note is in C language. To show the PMBus capabilities of ST7, a dedicated evaluation board is developed. This board consists of the ST72F264G1M6 microcontroller and it works with PC HyperTerminal. The objective of this demonstration board is to show to the user the features and capabilities of PMBus features using ST7 I2C peripheral, to support the standard PMBus commands. The results of this demonstration board interfaced with Artesyn's PMBus module are shown in this application note.

July 2008

Rev 2

1/44
www.st.com

Contents

AN2511

Contents
1 PMBus introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.1 PMBus protocol description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.1.1 1.1.2 SMBus version 1.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Extensions to SMBus version 1.1 specification . . . . . . . . . . . . . . . . . . . . 6

1.2

Hardwired signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.2.1 1.2.2 Electrical interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

2

Implementation of PMBus using ST7 I2C . . . . . . . . . . . . . . . . . . . . . . . . 8
2.1 Firmware architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.1.1 2.1.2 2.1.3 I2C initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Slave address and command code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Read and write operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

3

PMBus commands and source code . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3.1 3.2 3.3 3.4 PMBus commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Source code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 Limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

4

PMBus interfacing results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
4.1 4.2 Interfacing with Artesyn module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 Interfacing with SiLabs module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

5

PMBus demonstration board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
5.1 5.2 5.3 System requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Software setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Hardware setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

6

Using the demonstration board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
6.1 Normal operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
6.1.1 6.1.2 Selection of communication speed . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 Selection of packet error checking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

2/44

AN2511 6.1.3 6.1.4 6.1.5 6.1.6 6.1.7 6.1.8

Contents Selection of slave address . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 Selection of read/write mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 Single read mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 Continuous read mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 Write mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 Group command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

6.2

Error conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
6.2.1 6.2.2 Invalid command code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 Communication timeout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

7

Hardware description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
7.1 7.2 7.3 Schematic and layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 Bill of materials (BOM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 Demonstration board photo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

Appendix A Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
A.1 RS232 configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

Appendix B Index of supported PMBus commands . . . . . . . . . . . . . . . . . . . . . . 41 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

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List of tables

AN2511

List of tables
Table 1. Table 2. Table 3. Table 4. Table 5. Table 6. Table 7. Table 8. Table 9. Table 10. Table 11. Table 12. Table 13. Table 14. Table 15. Table 16. Table 17. Table 18. Table 19. Table 20. Table 21. Table 22. Table 23. Table 24. Table 25. Table 26. Table 27. Table 28. Table 29. Table 30. Table 31. Table 32. Table 33. Table 34. Table 35. Table 36. Table 37. Table 38. Table 39. Table 40. Table 41. Table 42. Table 43. Table 44. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 ON_OFF_CONFIG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 CLEAR_FAULTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 RESTORE_DEFAULT_ALL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 STORE_USER_ALL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 VOUT_MODE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 VOUT_COMMAND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 VOUT_MAX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 VOUT_MARGIN_HIGH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 VOUT_MARGIN_LOW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 VOUT_OV_WARN_LIMIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 VOUT_UV_WARN_LIMIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 IOUT_OC_FAULT_LIMIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 IOUT_OC_WARN_LIMIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 OT_FAULT_LIMIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 OT_FAULT_RESPONSE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 OT_WARN_LIMIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 TON_DELAY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 TON_RISE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 TOFF_DELAY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 TOFF_FALL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 STATUS_BYTE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 STATUS_WORD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 STATUS_VOUT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 STATUS_IOUT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 STATUS_TEMPERATURE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 STATUS_MFR_SPECIFIC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 READ_VOUT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 READ_IOUT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 READ_TEMPERATURE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 PMBUS_REVISION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 MFR_ID . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 MFR_MODEL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 MFR_REVISION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 MFR_LOCATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 MFR_DATE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 MFR_SERIAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 MFR_SPECIFIC_00 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 MFR_SPECIFIC_01 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 MFR_SPECIFIC_02 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 PMBus interfacing with Artesyn module: results. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 PMBus interfacing with SiLabs module: results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 Bill of material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

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AN2511

List of figures

List of figures
Figure 1. Figure 2. Figure 3. Figure 4. Figure 5. Figure 6. Figure 7. Figure 8. Figure 9. Figure 10. Figure 11. Figure 12. Figure 13. Figure 14. Figure 15. Figure 16. Figure 17. Figure 18. Figure 19. Figure 20. Figure 21. Figure 22. Figure 23. Figure 24. Figure 25. Figure 26. Figure 27. Figure 28. Figure 29. Figure 30. Interface diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Flowchart: I2C initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Flowchart: data length calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Flowchart: read operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Flowchart: write operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 PC HyperTerminal application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Baud rate configuration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 HyperTerminal settings - ASCII setup configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 HyperTerminal message to show company name and selection of communication speed 30 PEC selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 Slave address entry message . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 Wrong slave address entry - response 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 Wrong slave address entry - response 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 Options to select read/ write mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 Single read operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 Continuous read operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 Write mode command code entry message from HyperTerminal. . . . . . . . . . . . . . . . . . . . 32 Write mode data entry message from HyperTerminal . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 Write mode operation example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 Read operation to check data writing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 Group command code entry message from HyperTerminal . . . . . . . . . . . . . . . . . . . . . . . . 34 Group command operation example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 Invalid command message . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 Example of invalid command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 Communication timeout message . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 Demonstration board schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 Top view layout of the demonstration board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 Bottom view layout of the demonstration board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 STEVAL-ISQ002V1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 Pin description of RS232 D9 connector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

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PMBus introduction

AN2511

1
1.1

PMBus introduction
PMBus protocol description
The PMBus protocol is intended to cover a wide range of power system architectures and converters. PMBus devices must use the System Management Bus (SMBus), version 1.1. Implemented over the industry-standard SMBus serial interface, the PMBus protocol facilitates the programming, control and real-time monitoring of compliant power conversion products.

1.1.1

SMBus version 1.1
The System Management Bus (SMBus) is a two-wire interface through which various system component chips can communicate with each other and with the rest of the system. It is based on the principles of operation of I2C. For more information about SMBus, refer to AN1713, available from www.st.com.

1.1.2

Extensions to SMBus version 1.1 specification
1. Block write-block-read process call To support certain commands of the PMBus command language, PMBus devices must support the "Block write-block-read process call" described in Section 5.5.8 of Version 2.0 of the SMBus Specification. 2. Host notify protocol PMBus devices may support the host notify protocol described in Section 5.5.9 of Version 2.0 of the SMBus Specification. If a PMBus device supports the host notify protocol, the two data bytes sent to the host are the same as the data bytes returned by the STATUS_WORD command. 3. Group command protocol PMBus devices must support the group command protocol. The group command protocol is used to send commands to more than one PMBus device. The commands are received in one transmission. When the devices detect the STOP condition that ends the command, they all begin executing the command they received. 4. 5. Addressing PMBus devices use seven bit addresses. Packet error checking (PEC) Suppor t for the SMBus packet error checking (PEC) protocol is optional.

1.2
1.2.1

Hardwired signals
Electrical interface
The following diagram shows the interface between different PMBus devices. ST72264G1 is the selected microcontroller, which has a multi-master I2C interface. This microcontroller acts as PMBus master. It communicates with any compatible PMBus slave using a 4-pin interface. SMBC is the clock from the master. SMBD is the data pin. Both SMBC and SMBD should be pulled up with a 4.7 k resistor. SMBALERT is the SMBus alert pin, which helps

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AN2511

PMBus introduction the slave to alert the master whenever it wants to communicate. The control pin is used to switch ON or OFF a PMBus slave. Figure 1. Interface diagram
PMBus Master (ST72F264G1) SMBC (SCL) SMBD (SDA) SMBA (PA3) CONTROL (PC0) SMBC SMBD SMBA CONTROL PMBus Slave

The CONTROL signal is an input signal on a power converter. It is used to turn the unit on and off in conjunction with commands received via the serial bus. It can be configured as an active high or active low signal through the ON_OFF_CONFIG command (refer to Section 3.1). This signal is optional but recommended.

1.2.2

Timing
No specific requirements are made when a PMBus device must respond to a state change of a hardwired signal.

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Implementation of PMBus using ST7 I2C

AN2511

2
2.1

Implementation of PMBus using ST7 I2C
Firmware architecture
This section explains sequence of operation for different software modules.

2.1.1

I2C initialization
To use ST7 I2C for PMBus communication, the peripheral is initialized for 100 kHz communication speed. The I2C is configured with an address of 0x30, as it can act as a slave due to its multi-master capability. The following flowchart shows the sequence. Figure 2. Flowchart: I2C initialization
START

Initialize I2C CR, CCR, OAR1 and OAR2 registers

Configure slave addresses in OAR1 and OAR2

Enable I2C peripheral and acknowledge in I2CCR register

Set communication speed as 100kHz in I2CCCR register

STOP

The above flowchart is implemented in the function PMBus_Init.

2.1.2

Slave address and command code
The PMBus master addresses the slave with a 7-bit address. Once the slave device acknowledges the address, the command code is sent corresponding to the PMBus command and SMBus protocol (refer to Section 3.1). Then, the microcontroller decodes the command code as shown in the following sequence. Simultaneously, the SMBus_Mode variable is updated.

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AN2511 Figure 3.

Implementation of PMBus using ST7 I2C Flowchart: data length calculation
START

Check if command code equal to Block protocol No

Yes

Byte Count=6, Update SMBus_Mode for Block Command

Check if command code equal to Byte protocol

Yes

Byte Count=1, Update SMBus_Mode for Byte Command

No
Check if command code equal to word protocol No Yes Byte Count=2, Update SMBus_Mode for Word Command

STOP

Inside both PMBus_CommandRead and PMBus_CommandWrite functions, PMBus_DataLengthCalc is called which calculates the data length based on the command code received.

2.1.3

Read and write operation
PMBus master performs read/ write operations with the slave device. Depending on the command code, either PMBus_CommandRead or PMBus_CommandWrite is called. Inside this function, the SMBus transaction type is selected as shown in the following sequence. Figure 4. Flowchart: read operation
START

Check if SMBus_Mode for Byte command
1 S

Yes
7

SMBus Read byte protocol
1 Wr 1 A 8 Command Code 1 A 1 S 7 Slave Address 1 Rd 1 A 8 Data Byte 1 A 1 P

Slave Address

No Yes
1 S 7 Slave Address

Check if SMBus_Mode for Word command

SMBus Read word protocol
1 Wr 1 A 8 Command Code 1 A 8 Data Byte High 1 S 7 Slave Address 1 A 1 P 1 Rd 1 A 8 Data Byte Low 1 A ...

No

Check if SMBus_Mode for Send Block command
1

Yes
7

SMBus Read block protocol
1 Wr 1 A 8 Command Code 1 A 1 Sr 7 Slave Address 1 Rd 1 A 8 Count Byte = 1 1 A ...

No STOP

S

Slave Address

8 Data Byte 1

1 A

8 Data Byte 2

1 A

... ...

8 Data Byte N

1 A

1 P

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Implementation of PMBus using ST7 I2C Figure 5. Flowchart: write operation
START

AN2511

Check if SMBus_Mode for Send Byte command
1 S

Yes
7

SMBus Send byte protocol
1 Wr 1 A 8 Data Byte 1 A 1 P

Slave Address

No Yes SMBus Write byte protocol
1 S 7 Slave Address 1 Wr 1 A 8 Command Code 1 A 8 Data Byte 1 A 1 P

Check if SMBus_Mode for Write Byte command

Check if SMBus_Mode for Write Word command

Yes
1 S 7

SMBus Write word protocol
1 Wr 1 A 8 Command Code 1 A 8 Data Byte Low 1 A 8 Data Byte HIgh 1 A 1 P

Slave Address

No

Check if SMBus_Mode for Write Block command
1

Yes
7

SMBus Write block protocol
1 Wr 1 A 8 Command Code 1 A 8 Byte Count = N 1 Rd 1 A 8 Data Byte 1 1 A ...

No STOP

S

Slave Address

8 Data Byte 2

1 A

... ...

8 Data Byte N

1 A

1 P

During the PMBus communication, if there are any errors in communication (acknowledge failure, arbitration loss, bus error or SMBus timeout), the I2C peripheral is disabled. It is reinitialized again inside the PMBus write/ read functions. In case the SMBus Alert pin is pulled low by the slave to inform the master that it wants to communicate, the slave address is programmed with the alert response address (0x18). This is acknowledged by the slave that alerted the master. After the communication between the master and slave is complete, the slave address is programmed with the user-defined slave address. The default value of this user-defined address is 0x30. In case of group operation, the write operation flowchart is followed without the stop condition.

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PMBus commands and source code

3
3.1

PMBus commands and source code
PMBus commands
The Part II - command language document of PMBusTM Power System Management Protocol Specification v1.0 provides the list of PMBus commands. This driver supports the following list of commands. For each command a table is given. Table 1. Operation
OPERATION 01h The OPERATION command is used to turn the unit on and off in conjunction with the input from the CONTROL (OUTEN) pin. Read/ Write byte 1

Command name Command code Description SMBus transaction type Number of data bytes

Table 2.

ON_OFF_CONFIG
ON_OFF_CONFIG 02h The ON_OFF_CONFIG command configures the combination of CONTROL (OUTEN) pin input and serial bus commands needed to turn the unit on and off. Read/ Write byte 1

Command name Command code

Description

SMBus transaction type Number of data bytes

Table 3.

CLEAR_FAULTS
CLEAR_FAULTS 03h CLEAR_FAULTS is used to clear any fault bits that have been set. Send byte 0

Command name Command code Description SMBus transaction type Number of data bytes

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PMBus commands and source code Table 4. RESTORE_DEFAULT_ALL
RESTORE_DEFAULT_ALL 12h

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Command name Command code

Description

The RESTORE_DEFAULT_ALL command instructs the PMBus device to copy the entire contents of the non-volatile default store memory to the matching locations in the operating memory. Any items in default store that do not have matching locations in the operating memory are ignored. Send byte 0

SMBus transaction type Number of data bytes

Table 5.

STORE_USER_ALL
STORE_USER_ALL 15h The STORE_USER_ALL command instructs the PMBus device to copy the entire contents of the operating memory to the matching locations in the non-volatile user store memory. Any items in operating memory that do not have matching locations in the user store are ignored. Send byte 0

Command name Command code

Description

SMBus transaction type Number of data bytes

Table 6.

VOUT_MODE
VOUT_MODE 20h VOUT_MODE command, used for commanding and reading output voltage, consists of a three bit mode (only linear format is supported.) and a five-bit parameter representing the exponent used in output voltage Read/Writes. Read/ Write byte 1

Command name Command code

Description

SMBus transaction type Number of data bytes

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AN2511 Table 7. VOUT_COMMAND

PMBus commands and source code

Command name Command code Description SMBus transaction type Number of data bytes

VOUT_COMMAND 21h VOUT_COMMAND is used to set the output voltage, in volts (linear format). Read/ Write word 2

Table 8.

VOUT_MAX
VOUT_MAX 24h The VOUT_ MAX command sets an upper limit on the output voltage the unit can command regardless of any other commands or combinations. Read/ Write word 2

Command name Command code

Description

SMBus transaction type Number of data bytes

Table 9.

VOUT_MARGIN_HIGH
VOUT_MARGIN_HIGH 25h This VOUT_MARGIN_HIGH command loads the unit with the voltage to which the output is to be changed when the OPERATION command is set to "Margin High". Read/ Write word 2

Command name Command code

Description

SMBus transaction type Number of data bytes

Table 10.

VOUT_MARGIN_LOW
VOUT_MARGIN_LOW 26h This VOUT_MARGIN_LOW command loads the unit with the voltage to which the output is to be changed when the OPERATION command is set to "Margin Low". Read/ Write word 2

Command name Command code

Description

SMBus transaction type Number of data bytes

Table 11.

VOUT_OV_WARN_LIMIT
VOUT_OV_WARN_LIMIT 42h

Command name Command code

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PMBus commands and source code Table 11. VOUT_OV_WARN_LIMIT (continued)

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Description

The VOUT_OV_WARN_LIMIT command sets the value of the output voltage at the sense or output pins that causes an output voltage high warning. This value is typically less than the output overvoltage threshold. Read/ Write word 2

SMBus transaction type Number of data bytes

Table 12.

VOUT_UV_WARN_LIMIT
VOUT_UV_WARN_LIMIT 43h The VOUT_UV_WARN_LIMIT command sets the value of the output voltage at the sense or output pins that causes an output voltage low warning. This value is typically greater than the output undervoltage fault threshold Read/ Write word 2

Command name Command code

Description

SMBus transaction type Number of data bytes

Table 13.

IOUT_OC_FAULT_LIMIT
IOUT_OC_FAULT_LIMIT 46h The IOUT_OC_FAULT_LIMIT command sets the value of the sense output current, in amps (literal format), that causes an overcurrent fault. Read/ Write word 2

Command name Command code Description SMBus transaction type Number of data bytes

Table 14.

IOUT_OC_WARN_LIMIT
IOUT_OC_WARN_LIMIT 4Ah The IOUT_OV_WARN_LIMIT command sets the value of the output current that causes an output overcurrent warning. Read/ Write word 2

Command name Command code Description SMBus transaction type Number of data bytes

Table 15.

OT_FAULT_LIMIT
OT_FAULT_LIMIT 4Fh The OT_FAULT_LIMIT command sets the value of the sense temperature, in C (literal format), that causes an overtemperature fault

Command name Command code Description

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AN2511 Table 15. OT_FAULT_LIMIT (continued)

PMBus commands and source code

SMBus transaction type Number of data bytes

Read/ Write word 2

Table 16.

OT_FAULT_RESPONSE
OT_FAULT_RESPONSE 50h The OT_FAULT_RESPONSE command instructs the device on what action to take in response to an overtemperature fault. Read/ Write byte 1

Command name Command code Description SMBus transaction type Number of data bytes

Table 17.

OT_WARN_LIMIT
OT_WARN_LIMIT 51h The OT_WARN_LIMIT command sets the value of the sense temperature, in C (literal format), that causes an overtemperature warning. Read/ Write word 2

Command name Command code Description SMBus transaction type Number of data bytes

Table 18.

TON_DELAY
TON_DELAY 60h The TON_DELAY sets the time, in ms, from when a start condition is received (CONTROL signal asserted and a valid OPERATION command received) until the output voltage starts to rise. Read/ Write word 2

Command name Command code

Description

SMBus transaction type Number of data bytes

Table 19.

TON_RISE
TON_RISE 61h The TON_RISE sets the time, in ms, from when the output starts to rise until the voltage has entered the regulation band. Read/ Write word 2

Command name Command code Description SMBus transaction type Number of data bytes

Table 20.

TOFF_DELAY
TOFF_DELAY 64h

Command name Command code

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PMBus commands and source code Table 20. TOFF_DELAY (continued)

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Description

The TOFF_DELAY sets the time, in ms, from when a stop condition is received (CONTROL signal negated or a valid OPERATION command received) until the unit stops transferring energy to the output. Read/ Write word 2

SMBus transaction type Number of data bytes

Table 21.

TOFF_FALL
TOFF_FALL 65h The TOFF_FALL sets the time, in ms, from the end of the turnoff delay time until the voltage is commanded to zero. Note that this command can only be used with a device whose output can sink enough current to cause the output voltage to decrease at a controlled rate. Read/ Write word 2

Command name Command code

Description

SMBus transaction type Number of data bytes

Table 22.

STATUS_BYTE
STATUS_BYTE 78h The STATUS_BYTE command returns one byte of information with a summary of the most critical faults Read byte 1

Command name Command code Description SMBus transaction type Number of data bytes

Table 23.

STATUS_WORD
STATUS_WORD 79h The STATUS_WORD command returns two bytes of information with a summary of the units fault condition. Read word 2

Command name Command code Description SMBus transaction type Number of data bytes

Table 24.

:

STATUS_VOUT
STATUS_VOUT 7Ah The STATUS_VOUT commands returns one byte with status information on Vout.

Command name Command code Description

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AN2511 Table 24. STATUS_VOUT (continued)

PMBus commands and source code

SMBus transaction type Number of data bytes

Read byte 1

Table 25.

STATUS_IOUT
STATUS_IOUT 7Bh STATUS_IOUT commands returns one byte with status information on Iout. Read byte 1

Command name Command code Description SMBus transaction type Number of data bytes

Table 26.

STATUS_TEMPERATURE
STATUS_TEMPERATURE 7Dh STATUS_TEMPERATURE commands returns one byte with status information on temperature. Read byte 1

Command name Command code Description SMBus transaction type Number of data bytes

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PMBus commands and source code Table 27. STATUS_MFR_SPECIFIC
STATUS_MFR_SPECIFIC 80h

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Command name Command code Description SMBus transaction type Number of data bytes

STATUS_MFR_SPECIFIC commands returns one byte with the manufacturer specific status information. Read byte 1

Table 28.

READ_VOUT
READ_VOUT 8Bh The READ_VOUT command returns the actual measured output voltage in the same format as set by the VOUT_MODE command. Read word 2

Command name Command code Description SMBus transaction type Number of data bytes

Table 29.

READ_IOUT
READ_IOUT 8Ch The READ_IOUT command returns the measured output current in amperes. Read word 2

Command name Command code Description SMBus transaction type Number of data bytes

Table 30.

READ_TEMPERATURE
READ_TEMPERATURE 8Dh Up to three temperature readings can be returned for each device. Read word 2

Command name Command code Description SMBus transaction type Number of data bytes

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AN2511 Table 31. PMBUS_REVISION

PMBus commands and source code

Command name Command code Description SMBus transaction type Number of data bytes

PMBUS_REVISION 98h PMBUS_REVISION command stores or reads the revision of the PMBus to which the device is compliant. Read byte 1

Table 32.

MFR_ID
MFR_ID 99h The MFR_ID commands loads the unit with ASCII characters that contain the manufacturer's ID (name, abbreviation or symbol that identifies the unit's manufacturer). This is typically only done once at the time of manufacture. Read/Write block 7

Command name Command code

Description

SMBus transaction type Number of data bytes

Table 33.

MFR_MODEL
MFR_MODEL 9Ah The MFR_MODEL command loads the unit with ASCII characters that contain the manufacturer's model number. This is typically done once at the time of manufacture. Read/Write block 6

Command name Command code

Description

SMBus transaction type Number of data bytes

Table 34.

MFR_REVISION
MFR_REVISION 9Bh The MFR_REVISION command loads the unit with ASCII characters that contain the manufacturer's revision number. This is typically done once at the time of manufacture. Read/Write block 2

Command name Command code

Description

SMBus transaction type Number of data bytes

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PMBus commands and source code Table 35. MFR_LOCATION
MFR_LOCATION 9Ch

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Command name Command code

Description

The MFR_REVISION command loads the unit with ASCII characters that contain the manufacturer's revision number. This is typically done once at the time of manufacture. Read/Write block 2

SMBus transaction type Number of data bytes

Table 36.

MFR_DATE
MFR_DATE 9Dh The MFR_DATE command loads the unit with ASCII characters that identify the unit's date of manufacture. This is typically done once at the time of manufacture. Read/Write block 6

Command name Command code

Description

SMBus transaction type Number of data bytes

Table 37.

MFR_SERIAL
MFR_SERIAL 9Eh The MFR_SERIAL command loads the unit with a serial number to uniquely identify the unit Read/Write block 6

Command name Command code Description SMBus transaction type Number of data bytes

Table 38.

MFR_SPECIFIC_00
MFR_SPECIFIC_00 D0h The MFR_SPECIFIC_00 command provides access control for NVM register writes. Read byte 1

Command name Command code Description SMBus transaction type Number of data bytes

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AN2511 Table 39. MFR_SPECIFIC_01

PMBus commands and source code

Command name Command code Description SMBus transaction type Number of data bytes

MFR_SPECIFIC_01 D1h The MFR_SPECIFIC_01 command provides access control for configuration register writes. Read byte 1

Table 40.

MFR_SPECIFIC_02
MFR_SPECIFIC_02 D2h The MFR_SPECIFIC_02 is a manufacturer defined command. Read byte 1

Command name Command code Description SMBus transaction type Number of data bytes

3.2

Source code
The source code is attached in the zip file along with the application note. This source code is organized as shown below.
' Workspace directory ' Debug ' object files, list files, map files, executable files (.elf), hex code (.s19) ' Sources ' Main.c: Contains main source code. In this file, PMBus interface functions are called (refer to section 3.3). ' Main.h: Contains prototype of all functions used in Main.c. ' PMBus.c: Contains functions for PMBus write and read operation. The data length calculator function and I2C and Alert signal interrupt subroutines are also written inside this file. ' PMBus.h: Contains prototype of all functions and enumerated data types used in PMBus.c. ' SMBus_Master.c: Contains source code for differnet SMBus master transaction bus protocols. ' SMBus_Master.h: Contains prototype of all functions and enumerated data types used in SMBus_Master.c. ' st72264g1.h: Contains register mapping for ST72F264G1 device. ' ST7_hr.h: Contains hardware register bit definitions for ST7 MCU ' ST7_Config.h: Contains compiler selection, peripheral register inclusion, header files inclusion for linking, macros for assembly instructions and Fcpu Definition. ' interrupt_vector.c: Contains general Interrupt vector table for ST7 devices

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PMBus commands and source code

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3.3

Example
This section explains how to use the PMBus driver. An example operation of write/ read commands are shown.
/* * ** * ** * ** * ** * ** * ** * ** * ** * ** * ** * ** * ** * ** * ** * *** COPYRIGHT 2005 STMicroelectronics Source File Name : Main.c Group : IMS Systems Lab Author : Telecom Team Date First Issued: 01/09/2006 -*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*THE SOFTWARE INCLUDED IN THIS FILE IS FOR GUIDANCE ONLY. STMicroelectronics SHALL NOT BE HELD LIABLE FOR ANY DIRECT, INDIRECT OR CONSEQUENTIAL DAMAGES WITH RESPECT TO ANY CLAIMS ARISING FROM USE OF THIS SOFTWARE. -*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-* * ** * ** * ** * ** * ** * ****Documentation* * ** * ** * ** * ** * ** * ***** General Purpose - Contains main source code. In this file, the PMBus command files are written. * * ** * ** * ** * ** * ** * ** * ** * ** * ** * ** * ** * ** * ** * ** * ****/ #include "ST7_config.h" /* Fcpu defined as 8MHz */ #include "main.h" /* Contains the global variables used in main.c */ #include "ST7_hr.h" /* Contains the register and flags for ST7 */ extern volatile unsigned int SMB_TimeCount; /* Time count variable */

#pragma space extern [] @tiny /* To force following variables into short addressing memory */ extern unsigned char Data_Buff [32] ; /* Buffer to store data */ /* Variables to differentiate the different SMBus transaction types */ extern volatile unsigned char SMBus_Mode ; extern volatile unsigned char SMB_Err_Status ; /* Error status */ /* Master to address slave with this

address */ static volatile unsigned char PMBus_SlaveAdd = 0x80; /* Master to address slave with this address */ static volatile unsigned char PMBus_SlaveAdd = 0x80; /*----------------------------------------------------------------------------ROUTINE NAME : Main INPUT : None OUTPUT : None DESCRIPTION : Using this file, user can write/ read PMBus commands. COMMENTS : Programs jumpts into this routine when microcontroller is reset -----------------------------------------------------------------------------*/ void main() { unsigned char temp ; SMBs_Address_t PMBus_Err ; /* To check errors in PMBus communication */ /*----------------------- Port A configuration ----------------------------*/ PADDR &= (unsigned char)~PORTA_DEFAULT; PADDR = PORTA_DEFAULT ; /* Other pins configured as floating input */ PAOR = (unsigned char)(PORTA_DEFAULT) ; /*----------------------- Port C configuration ----------------------------*/ PCDDR = CONTROL ; /* PC0 floating input, others push pull output */

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PCOR = CONTROL ; PCDR = CONTROL ;

PMBus commands and source code

/*----------------------- Alert Interrupt configuration ------------------------------*/ EnableInterrupts; /* Resets interrupt mask */ MISCR1 = 0x10 ; /* EI0 on falling edge low level for Alert interrupt */

/*---------------------PMBus communication configuration-------------------*/ while (1) { /* I2C configuration: ST7 I2C address 0x30, communication speed 100kHz */ PMBus_Init (SMBs_MISC, SLAVEADD, 0x40, 0x23); /* Checking if an alert signal is received from slave */ if (SMBus_Mode & SMB_ARA) { /* ST7 I2C sends the alert response address to check which slave alerted */ PMBus_Err = SMBm_ReceiveByte (ALERTRESPONSEADD, Data_Buff); /* Alerted slave address will be used for any further communication */ PMBus_SlaveAdd = *Data_Buff ; SMBus_Mode &= (unsigned char) ~SMB_ARA ; } Command_Code = 0x01; /* User should enter the PMBus command code here */ PMBus_CommandWrite (Command_Code); /* Writes data from Data_Buff */

Command_Code =

0x02; /* User should enter the PMBus command code here */ /* Read data and store it in Data_Buff */ PMBus_CommandRead (Command_Code); if (SMB_Err_Status) { errors */ SMB_Err_Status = I2CSR2 ; SMB_Err_Status = 0 ; } } }

/* I2C status register read to clear any

/* End of while (1) */ /* End of main */

3.4

Limitations
1. 2. 3. The SMBus driver used in this application note is tested only for write word, read word and write block protocols with PEC disabled. The SMBus driver doesn't meet the clock low extending feature of SMBus v1.1 due to the limitation of the I2C peripheral. In case of PEC, when slave is acting as receiver, the ACK bit is not disabled if the PEC received from master transmitter is different from slave. It is stored in the user address as the last byte. It is the responsibility of the user to check the master PEC with the slave PEC to decide on data validity.

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PMBus interfacing results

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4

PMBus interfacing results
This section describes the results of interfacing the demonstration board with Artesyn and SiLabs modules.

4.1

Interfacing with Artesyn module
The following table shows the different PMBus commands and ST demonstration board results compared to the Artesyn DPL20C PMbus module. Table 41.
Command code 01 02 03 12 15 20 21 24 25 26 42 43 46 4A 4F 50 51 60 61 64 65

PMBus interfacing with Artesyn module: results
PMBus command OPERATION ON_OFF_CONFIG CLEAR_FAULTS RESTORE_DEFAULT_ ALL STORE_USER_ALL VOUT_MODE VOUT_COMMAND VOUT_MAX VOUT_MARGIN_HIGH VOUT_MARGIN_LOW VOUT_OV_WARN_LIM IT VOUT_UV_WARN_LIM IT IOUT_OC_FAULT_LI MIT IOUT_OC_WARN_LIM IT OT_FAULT_LIMIT OT_FAULT_RESPONS E OT_WARN_LIMIT TON_DELAY TON_RISE TOFF_DELAY TOFF_FALL SMBus transaction type Read/ Write byte Read/ Write byte Send byte Send byte Send byte Read/ Write byte Read/ Write word Read/ Write word Read/ Write word Read/ Write word Read/ Write word Read/ Write word Read/ Write word Read/ Write word Read/ Write word Read/ Write byte Read/ Write word Read/ Write word Read/ Write word Read/ Write word Read/ Write word Number of data bytes 1 1 0 0 0 1 2 2 2 2 2 2 2 2 2 1 2 2 2 2 2 1A 00 60 01 60 00 6 A 00 56 00 6E 00 56 00 19 00 17 00 78 B1 00 6E 00 00 00 0A 00 00 00 00 1A 00 60 01 60 00 6 A 00 56 00 6E 00 56 00 19 00 17 00 78 B1 00 6E 00 00 00 0A 00 00 00 00 Data (Si8250) 80 14 Data (ST7) 80 14

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AN2511 Table 41.
Command code 78 79 7A 7B 7D 80 8B 8C 8D 98 99

PMBus interfacing results PMBus interfacing with Artesyn module: results (continued)
PMBus command STATUS_BYTE STATUS_WORD STATUS_VOUT STATUS_IOUT STATUS_TEMPERATU RE STATUS_MFR_SPECI FIC READ_VOUT READ_IOUT READ_TEMPERATURE PMBUS_REVISION MFR_ID SMBus transaction type Read byte Read word Read byte Read byte Read byte Read byte Read word Read word Read word Read byte Read block Number of data bytes 1 2 1 1 1 1 2 2 2 1 7 Data (Si8250) 41 00 41 00 00 00 02 00 01 D7 C3 00 20 01 Data (ST7) 41 00 41 00 00 00 02 00 01 D7 C3 00 1D 01

41 52 54 41 52 54 45 45 53 59 53 59 4E 4E 44 50 4C 32 44 50 4C 30 43 32 30 43 31 02 5A 02 31 41 5A 53

9A 9B 9C 9D 9E D0 D1 D2

MFR_MODEL MFR_REVISION MFR_LOCATION MFR_DATE MFR_SERIAL MFR_SPECIFIC_00 MFR_SPECIFIC_01 MFR_SPECIFIC_02

Read block Read/ Write block Read/ Write block Read/ Write block Read/ Write block Read byte Read byte Read byte

6 2 2 6 6 1 1 1

32 34 30 33 32 34 30 36 06 33 36 36 31 32 33 34 31 32 33 35 06 34 35 36 28 10 0A 28 10 0A

4.2

Interfacing with SiLabs module
The following table shows the different PMBus commands and ST demonstration board results compared to Silicon Labs Si8250 - TB module. Table 42.
Command code 01 02

PMBus interfacing with SiLabs module: results
PMBus command OPERATION ON_OFF_CONFIG SMBus transaction type Read/ Write byte Read/ Write byte Number of data bytes 1 1 Data (Si8250) C0 1E Data (ST7) C0 1E

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PMBus interfacing results Table 42.
Command code 03 12 15 20 21 24 25 25 26 42 43 4F 50 51 60 61 64 65 78 79 7A 7B 7D 80 8B 8C 8D 98 D0 D1 D2

AN2511

PMBus interfacing with SiLabs module: results (continued)
PMBus command CLEAR_FAULTS RESTORE_DEFAULT_ALL STORE_USER_ALL VOUT_MODE VOUT_COMMAND VOUT_MAX VOUT_MARGIN_HIGH VOUT_MARGIN_HIGH VOUT_MARGIN_LOW VOUT_OV_WARN_LIMIT VOUT_UV_WARN_LIMIT OT_FAULT_LIMIT OT_FAULT_RESPONSE OT_WARN_LIMIT TON_DELAY TON_RISE TOFF_DELAY TOFF_FALL STATUS_BYTE STATUS_WORD STATUS_VOUT STATUS_IOUT STATUS_TEMPERATURE STATUS_MFR_SPECIFIC READ_VOUT READ_IOUT READ_TEMPERATURE PMBUS_REVISION MFR_SPECIFIC_00 MFR_SPECIFIC_01 MFR_SPECIFIC_02 SMBus transaction type Send byte Send byte Send byte Read/ Write byte Read/ Write word Read/ Write word Read/ Write word Read/ Write word Read/ Write word Read/ Write word Read/ Write word Read/ Write word Read/ Write byte Read/ Write word Read/ Write word Read/ Write word Read/ Write word Read/ Write word Read byte Read word Read byte Read byte Read byte Read byte Read word Read word Read word Read byte Read byte Read byte Read byte Number of data bytes 0 0 0 1 2 2 2 2 2 2 2 2 1 2 2 2 2 2 1 2 1 1 1 1 2 2 2 1 1 1 1 11 7F F6 89 94 00 6A 86 5C 79 90 89 94 76 58 EB 20 00 EA D0 00 0A 00 32 00 0A 00 C8 04 00 04 00 00 20 00 80 4E D7 C3 EF 56 00 67 EF 08 11 7F F6 89 94 00 6A 86 5C 79 90 89 94 76 58 EB 20 00 EA D0 00 0A 00 32 00 0A 00 C8 04 00 04 00 00 20 00 80 76 00 00 EF 56 00 67 EF 08 Data (Si8250) Data (ST7)

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AN2511

PMBus demonstration board

5

PMBus demonstration board
To show the features of the ST7 I2C working as a PMBus, a demonstration board is available on request. Please contact the nearest ST office to get this board. The evaluation board has an ST72F264G1 MCU that has 4 KBytes Flash memory. All PMBus functionalities are not shown, as this evaluation board has HyperTerminal interface which requires lot of messages to be stored in program memory.

5.1

System requirements
In order to use the PMBus demonstration board with the Windows operating system. The PC should support HyperTerminal software and RS232 communication using DB9 connector.

5.2

Software setup
To configure the PC HyperTerminal software, the user should follow the steps as mentioned below. 1. Click on Start -> Programs -> Accessories -> Communications -> HyperTerminal as shown below. PC HyperTerminal application

Figure 6.

2. 3.

Select the correct port in which RS232 (9-pin cable) is connected (refer to Section 3). Configure the following baud rate (bits per second) in HyperTerminal: File -> Properties -> Connect to -> Configure. If the user configures any baud rate other than 38400, then RS232 communication fails.

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PMBus demonstration board Figure 7. Baud rate configuration

AN2511

4.

Configure the following settings in HyperTerminal: File -> Properties -> Settings -> ASCII setup HyperTerminal settings - ASCII setup configuration

Figure 8.

5.

Press Call in HyperTerminal to establish a connection with the board.

5.3

Hardware setup
To configure the hardware board, the user should follow these steps: 1. Jumper settings: There are four jumpers (JP1, JP2, JP3 and JP4) available on the board. The detail of these connectors is as follows: a) JP1: JP1 pins should be connected using the jumper if there is no pull-up connected in the clock line of the I2C bus. Once connected, the I2C clock line is pulled up with a resistor value of 4.7 k. JP2: JP2 pins should be connected using the jumper if there is no pull-up connected in the data line of the I2C bus. Once connected, the I2C data line is pulled up with a resistor value of 4.7 k. JP3: JP3 is used to select the clock source for the ST7 microcontroller. From the JP3 side, if the jumper is connected between pins 1 and 2 then the application

b)

c)

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AN2511

PMBus demonstration board runs using the resonator clock (16 MHz). If the jumper is connected between pins 2 and 3 then the application is stopped and ST7 MCU can be re-programmed. d) JP4: JP4 is used to select the power supply as described below. From the JP4 side, if the jumper is connected between pins 2 and 3 then the application runs using the direct supply given from `POWER' connector. If the jumper is connected between pins 1 and 2 then the application runs using the DC adapter supply given from J1.

2.

Power settings: The demonstration board can be powered by one of the following options: a) DC adapter: Connect a DC adapter to J1. The DC adapter should supply a minimum of 7 V and maximum of 18 V, 1 A. This supply is regulated to 5 V supply using an L7805 regulator. Regulated supply: The user can use a direct 3 V to 5 V supply. The supply and Gnd points should be connected to the `POWER' connector pins 1 and 2. Here, `POWER' connector pin 1 is referred from the JP4 jumper side (from the right side).

b)

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Using the demonstration board

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6

Using the demonstration board
After installing the setup as explained in Section 1, the following message appears in HyperTerminal. Figure 9. HyperTerminal message to show company name and selection of communication speed

If there is any problem in getting the message, press the switch provided in the demonstration board. This switch re-starts the application.

6.1

Normal operation
The following sections explain how to initiate PMBus communication and how to read/ write PMBus commands with HyperTerminal.

6.1.1

Selection of communication speed
After the message appears as shown in Figure 9, the user should enter 1 or 2 to select the PMBus communication speed as 100 kHz or 400 kHz respectively. The default speed value selected is 100 kHz. If the user enters any other value other than 1 and 2, the previous speed value is retained.

6.1.2

Selection of packet error checking
After the message appears as shown in Figure 10, the user should enter 1 or 2 to enable PEC and disable PEC respectively. If PEC is enabled, all address, command code and data communications are checked through CRC-8 check. The default PEC value is PEC disabled. If the user enters any other value other than 1 and 2, the previous speed value is retained. Figure 10. PEC selection

6.1.3

Selection of slave address
The user should enter the slave address of the PMBus device. The slave address should be in hexadecimal format. The slave addresses of different competitor's module are given below. Artesyn DPL20C module: 0x30 SiLabs Si8250-TB module : 0x80. The slave address could change from one device to another device. The user must refer to the product datasheet and development kit documents to decide on the slave address. An example entry of slave address with Artesyn DPL20C module is shown below.

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AN2511 Figure 11. Slave address entry message

Using the demonstration board

If the user enters a wrong slave address then one of the following error messages shown in Figure 12 or Figure 13 appears. Figure 12. Wrong slave address entry - response 1

Figure 13. Wrong slave address entry - response 2

6.1.4

Selection of read/write mode
Data can be written into or data can be read back from the PMBus salve device connected. The following figure provides the key option to select one of the modes. Figure 14. Options to select read/ write mode

6.1.5

Single read mode
The user can press 1 to select read mode. Then the user can enter any command code with reference to Section 3 to read byte/ word/ block of data. An example of this is shown below. Figure 15. Single read operation

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Using the demonstration board

AN2511

6.1.6

Continuous read mode
The user can press 0 to read all PMBus commands. The lists of supported commands are shown in the following figure. Figure 16. Continuous read operation

Command codes 0xD0, 0xD1 and 0xD2 are not supported in continuous read mode. If the user wants to read these commands, they can be read by using single read mode.

6.1.7

Write mode
The user can press 2 to select write mode. After the following figure appears, the user can enter any command code with reference to Section 2.1 on page 8 to write byte/ word/ block of data. Figure 17. Write mode command code entry message from HyperTerminal

Then the user can enter any command code with reference to Section 4 to write byte/ word/ block of data. The user can enter data after the following message. Figure 18. Write mode data entry message from HyperTerminal

Data should be entered in hex format. If the user wants to enter date/ serial numbers, they should be entered in ASCII format.

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AN2511

Using the demonstration board For example, to enter a date as "15 -12-1991", then data should be entered as 313531323931 (where 31h=ASCII "1", 35h=ASCII "5", etc., and the date will read "151291"). An example of this operation is shown below. Figure 19. Write mode operation example

When reading back the date written using single read commands, the following message is displayed: Figure 20. Read operation to check data writing

6.1.8

Group command
The user can press 3 to select group command mode. In this demonstration board, the user can write multiple commands for multiple slave addresses. After Figure 21 appears, the user can enter any command code and data with reference to Section 3.1: PMBus commands to write byte/ word/ block of data. The user can enter 5 commands and data for the group command. If the user wants to write less than 5 commands, the user can press * to terminate the group command operation.

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Using the demonstration board Figure 21. Group command code entry message from HyperTerminal

AN2511

An example of this operation is shown below. Figure 22. Group command operation example

6.2

Error conditions
The following error conditions may be encountered during PMBus communication.

6.2.1

Invalid command code
If the user enters a command code that is not available in the list or enters an incorrect option to select read/write options, the following error message appears: Figure 23. Invalid command message

An example is shown in Figure 24.

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AN2511 Figure 24. Example of invalid command

Using the demonstration board

6.2.2

Communication timeout
This error appears when the PMBus communication fails due to one of the following reasons:

The slave device doesn't acknowledge the master The clock low interval exceeds the value of TTIMEOUT,MIN as defined by (SMBus Specification 1.1) TLOW:SEXT and TLOW:MEXT conditions are not met Bus error or arbitration errors in PMBus communication

In these conditions, the following error message appears: Figure 25. Communication timeout message

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Hardware description

AN2511

7

Hardware description
This section provides schematics, BOM (bill of materials), layout and picture of the demonstration board.

7.1

Schematic and layout
The following figures show the schematic and layouts of the demonstration board. Figure 26. Demonstration board schematic

0,&52&21752//(5

32:(5 6833/<

56 ,17(5)$&(

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&211(&7256

,&& &211(&725

AN2511 Figure 27. Top view layout of the demonstration board

Hardware description

Figure 28. Bottom view layout of the demonstration board

7.2
Table 43.

Bill of materials (BOM)
The following table shows the BOM of the demonstration board. Bill of material
Value / generic Qty part number Manufacturer Manufacturer's ordering code / orderable part number
Table 43:

Index

Reference

Package

Supplier

1 2 3 4 5

Capacitors: C2, C3, C9, C10, C11, C12, C13 Capacitors: C7, C8 Capacitors: C5, C6 Capacitors: C1 Polarized Capacitor (Axial): C4

7 2 2 1 1

100 nF 10 nF 10 pF 330 nF 100 F/ 10 V

805 805 805 805 RB-5.5

Any Any Any Any Any

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Hardware description Table 43. Bill of material (continued)
Value / generic Qty part number 3 2 1 1 1 6 2 1 1 1 1 1 1 1 1 1 1 1 1 1 4.7 k 100 220 10 k CON1 CON2 CON3 CON4 CON7 DB9 16 MHz (KDS) ICC JACK L7805CD2T-TR SMD LED ST72F264G1M6 ST3232CTR TACT SWITCH 1N5817 SMAJ20A-TR Manufacturer Any Any Any Any Any Any Any Any Any Manufacturer's ordering code / orderable part number

AN2511

Index

Reference

Package

Supplier

6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

Resistors: R1, R2, R3 Resistors: R4, R5 Resistors: R6 Resistors: R7 Connector : TP3 Connectors: J2, J3, J4, JP1, JP2, POWER Connectors: JP3, JP4 Connector: J5 Connector J7 9 Pin Female RS232 connector: J6 Crystal: Y1 Header: CON1 Power Jack connector: J1 Regulator : U1 SMD LED: D1 MCU U2 RS232 level translator: U3 Switch S1 Diode: D2 ZENER diode: ZD1

805 805 805 805 SIP-1 SIP-2 SIP-3 SIP-4 SIP-7 DB9/F XTAL-1 IDC-10B TAP_2.5 mm TO-220 LED-SMD SOL-28 SO-16 PUSH-4 DO41 TO220

GM (801-036) Any Any GM: K375A ST Faichild ST ST Any ST ST ST72F264G1M6 ST3232CTR L7805CD2T-TR

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AN2511

Hardware description

7.3

Demonstration board photo
The following figure shows the picture of the demonstration board. Figure 29. STEVAL-ISQ002V1

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Configuration

AN2511

Appendix A
A.1

Configuration

RS232 configuration
The following figure shows the pin description of the RS232 D9 connector. Figure 30. Pin description of RS232 D9 connector

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AN2511

Index of supported PMBus commands

Appendix B
C

Index of supported PMBus commands

CLEAR_FAULTS . . . . . . . . . . . . . . . . . . . . . . . . 9

I
IOUT_OC_FAULT_LIMIT . . . . . . . . . . . . . . . . 1 2 IOUT_OC_WARN _LIMIT . . . . . . . . . . . . . . . . . 1 2

M
MFR_DATE . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 MFR_ID . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 MFR_LOCATION . . . . . . . . . . . . . . . . . . . . . . . 18 MFR_MODEL . . . . . . . . . . . . . . . . . . . . . . . . . 17 MFR_REVISION . . . . . . . . . . . . . . . . . . . . . . . 17 MFR_SERIAL . . . . . . . . . . . . . . . . . . . . . . . . . 18 MFR_SPECIFIC_00 . . . . . . . . . . . . . . . . . . . . 18 MFR_SPECIFIC_01 . . . . . . . . . . . . . . . . . . . . 19 MFR_SPECIFIC_02 . . . . . . . . . . . . . . . . . . . . 19

O
ON_OFF_CONFIG . . . . . . . . . . . . . . . . . . . . . . 9 OPE RATIO N . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 OT_FAULT_LIMIT . . . . . . . . . . . . . . . . . . . . . . 13 OT_FAULT_RESPONSE . . . . . . . . . . . . . . . . 13 OT_WARN_LIMIT . . . . . . . . . . . . . . . . . . . . . . 13

P
PMBUS_REVISION . . . . . . . . . . . . . . . . . . . . . 1 7

R
READ _IOUT . . . . . . . . . . . . . . . . . . . . . . . . . . 1 6 READ _TEMPERATUR E . . . . . . . . . . . . . . . . . 1 6 READ _VOUT . . . . . . . . . . . . . . . . . . . . . . . . . . 1 6 RESTORE_DEFAULT_ALL . . . . . . . . . . . . . . . 1 0

S
STATUS_BYTE . . . . . . . . . . . . . . . . . . . . . . . . 1 4 STATUS_IOU T . . . . . . . . . . . . . . . . . . . . . . . . 1 5 STATUS_MFR_SPEC IFIC . . . . . . . . . . . . . . . 1 6 STATUS_TEMPER ATURE . . . . . . . . . . . . . . . 1 5 STATUS_VOU T . . . . . . . . . . . . . . . . . . . . . . . . 1 5 STATUS_WOR D . . . . . . . . . . . . . . . . . . . . . . . 1 5 STOR E_U SER_ALL . . . . . . . . . . . . . . . . . . . . 1 0

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Index of supported PMBus commands

AN2511

T
TOFF_DELAY . . . . . . . . . . . . . . . . . . . . . . . . . 14 TOFF_FALL . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 TON_DELAY . . . . . . . . . . . . . . . . . . . . . . . . . . 1 3 TON_RISE . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 4

V
VOU T _COMMAND . . . . . . . . . . . . . . . . . . . . . 1 1 VOU T _MARGIN_HIGH . . . . . . . . . . . . . . . . . . 1 1 VOU T _MARGIN_LOW . . . . . . . . . . . . . . . . . . 1 1 VOU T _MAX . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1 VOU T _MODE . . . . . . . . . . . . . . . . . . . . . . . . . 1 0 VOU T _OV_W A RN_LIMIT . . . . . . . . . . . . . . . . 1 2 VOUT_UV_WARN_LIMIT . . . . . . . . . . . . . . . . 12

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AN2511

Revision history

Revision history
Table 44.
Date 17-Apr-2007

Document revision history
Revision 1 Initial release. Modified: Figure 9, 10, 16, 17, 18, 19, 20, 23, 24, 25, 26, 29, Table 43 Added: Figure 27, 28 Minor text changes Changes

18-Jul-2008

2

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AN2511

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