Application Guide - XMC4000 - Power Management Bus (PMBus) Slave

XMC 400 0
Microcontroller Series for Industrial Applications
Po wer Ma nage m ent Bus ( P M Bus )
Sla ve D e vice wi th X M C40 00
Applic atio n Guid e
V1.1 2014-03
Mic rocon t rolle rs
Edition 2014-03
Published by Infineon Technologies AG,
81726 Munich, Germany.
© 2014 Infineon Technologies AG
All Rights Reserved.
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Power Management Bus (PMBus) Slave Device with XMC4000
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Last Trademarks Update 2011-11-11
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Power Management Bus (PMBus) Slave Device with XMC4000
Revision History
Date
Version
Change Description
July 2013
1.0
Initial release
March 2014
1.1
− I2C001 app replaced by I2C003 app
− Update Table 7 ’List of DAVE
TM
Apps used’
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Table of Contents
Revision History .................................................................................................................................................... 4
Table of Contents .................................................................................................................................................. 5
1
1.1
1.2
1.3
1.3.1
1.3.2
1.3.3
1.3.4
1.3.5
1.3.6
1.4
Overview ............................................................................................................................................ 6
System Overview ................................................................................................................................ 6
PMBus Features.................................................................................................................................. 7
PMBus Protocols ................................................................................................................................. 7
Send Byte ............................................................................................................................................ 8
Write Byte ............................................................................................................................................ 8
Write Word .......................................................................................................................................... 9
Read Byte ............................................................................................................................................ 9
Read Word ........................................................................................................................................ 10
Host Notify ......................................................................................................................................... 10
PMBus Commands and Data Formats ............................................................................................. 11
2
2.1
2.2
2.2.1
2.2.2
2.2.2.1
2.2.2.2
2.2.2.3
2.2.2.4
2.2.3
2.2.4
2.3
2.3.1
2.3.2
Implementation of PMBus Slave on XMC4500 ............................................................................. 12
Hardware ........................................................................................................................................... 13
Software ............................................................................................................................................ 14
Software Flow.................................................................................................................................... 15
Software API Functions ..................................................................................................................... 16
PMBus Protocol Layer Interface API Functions ................................................................................ 16
2
I C Transport Layer Interface API Functions .................................................................................... 16
Data Storage API Functions .............................................................................................................. 17
Interrupt Handlers.............................................................................................................................. 17
Packet Error Checking (PEC) ........................................................................................................... 17
Fault Reporting Mechanism .............................................................................................................. 17
Implementation Consideration .......................................................................................................... 18
How to modify a response for a command ....................................................................................... 18
How to add a command .................................................................................................................... 19
3
3.1
3.1.1
3.2
Application Example ....................................................................................................................... 20
Getting Started .................................................................................................................................. 20
Hardware Setup ................................................................................................................................ 20
XMC4500 PMBus Software Package for Slave Device .................................................................... 22
4
Conclusion ....................................................................................................................................... 23
5
References ....................................................................................................................................... 24
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Overview
1
Overview
The Power Management Bus (PMBus™) is a free and open standard power-management protocol with a fully
defined command language that facilitates communication with power converters and other devices in a power
system. It is a variant of System Management Bus (SMBus), and is a relatively slow speed, two-wire
communications protocol based on the Inter-Integrated Circuit Bus (I²C). The PMBus standard defines over two
hundred commands, and a substantial number of the commands are specifically for power conversion
processes..
This application guide gives details of the PMBus standard and describes the implementation of the protocol on
the Slave Device using the Infineon XMC4500 microcontroller. The XMC4500 microcontroller belongs to the
XMC4000 industrial family based on the ARM Cortex-M4 processor core. The Universal Serial Interface
Channel module (USIC) contained in the microcontroller is a flexible interface module covering several serial
communication protocols including the Inter-Integrated Circuit (I²C).
1.1
System Overview
PMBus consists of a single host and multiple devices. It is a two-line communication protocol based on I²C.
There are two optional lines, SMBALERT and CONTROL line.
Figure 1
PMBus communication architecture
Note: The SMBALERT# and CONTROL signals are optional to the operation of PMBus system. The PMBus
2
system can function with the two serial bus lines (I C).
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Overview
2
I C Serial Bus line
2
The Serial Bus Data and Serial Bus Clock line perform I C functions. These two are essential lines for the
PMBus functionality.
SMBALERT# Signal
The SMBALERT signal line is a an interrupt line for slave-only devices to notify the Host. The Slave can signal
the Host through the SMBALERT line when a fault occurs and has to be reported.
The Host will process the interrupt and access all the SMBALERT# devices using Alert Response Address and
the devices that assert the signal will respond to the alert response address.
CONTROL Signal
The CONTROL signal is an output signal on a PMBus Host. It can use this signal in conjunction with commands
via the serial bus to turn the Slave Device on or off.
1.2
PMBus Features
The following features are recommended to improve the communication and data reliability, to create a robust
PMBus system.
Timeout Mechanism
The PMBus system adopts a timeout mechanism to resume the functionality if fault conditions happen. If the
clock line is held low longer than a certain time, the device must reset the communication to resume normal
functionality.
Fault Reporting
The Slave Device is required to report the fault conditions to the Host during operation. The report can be via;

the SMBALERT# signal

using the host-notify protocol (section 1.3.6).
Packet Error Checking (PEC)
An optional Packet Error Checking (PEC) feature is recommended, in order to significantly increase the data
reliability. PEC checks the reliability of the received data packets via a cyclic redundancy check-8 (CRC-8)
algorithm.
1.3
PMBus Protocols
In the XMC4500 implementation, the following types of PMBus command packet structures are supported:

Send Byte

Write Byte

Write Word

Read Byte

Read Word

Host Notify
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Overview
1.3.1
Send Byte
This is used by the Host (the PMBus master) to send a command to the Slave Device to perform simple tasks
that do not require any data bytes.
For example, the CLEAR_FAULTS command is used to clear all the fault flags in the system.
The Host starts the communication by generating a start condition(S); write a 7 bit slave address with a write bit,
followed by the 8 bit command.
The Slave will acknowledge each byte received (shaded portion in the figure).
The communication is terminated by a stop condition (P) generated by the Host.
The additional PEC byte ensures data reliability.
Figure 2
Send Byte Packet without PEC
Figure 3
Send Byte Packet with PEC
1.3.2
Write Byte
Used by the Host to write a one-byte value to certain variables in Slave Device settings.
For example, VOUT_MODE command can be used to change the voltage representation by writing a new
variable value.
Figure 4
Write Byte Packet without PEC
Figure 5
Write Byte Packet with PEC
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Overview
1.3.3
Write Word
Used to write one word (2 bytes) of information into the Slave Device variable.
Figure 6
Write Word Packet without PEC
Figure 7
Write Word Packet with PEC
1.3.4
Read Byte
This is used by the Host to read one byte of information from the Slave Device.
For example, the STATUS_BYTE command enables the Host to read the error status of the Slave Device.
As shown in the figure, after the acknowledgement for command code from the Slave, the Host sends a
repeated start (Sr) condition, followed by the 7-bit address with a read bit. The Slave will then acknowledge and
send out one byte data.
Figure 8
Read Byte Packet without PEC
Figure 9
Read Byte Packet with PEC
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Overview
1.3.5
Read Word
Used for the Host to read one word of data from the PMBus Slave Device.
For example, the READ_TEMPERATURE_1 command is used to read the temperature of the Slave Device.
Figure 10
Read Word Packet without PEC
Figure 11
Read Word Packet with PEC
1.3.6
Host Notify
When fault condition occurs in the Slave, the Slave needs to report the error back to the Host. In this case, the
Slave Device becomes the bus master and initiates a communication session using the host notify protocol. The
Slave Device address and two-byte status information are transmitted to the Host.
Figure 12
Host Notify Protocol
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Overview
1.4
PMBus Commands and Data Formats
The PMBus commands are one byte command codes. They consist of output voltage related commands, fault
related commands, read status command and parametric write/read commands. With these commands the
Host can configure the Slave Device peripherals and read the status.
To support the write/read of the parametric data (except for output voltage), data is mainly represented in 2
types of format:

LINEAR

DIRECT
For output voltage and output voltage related parameter, they are represented in three formats:

LINEAR scale using 2 bytes unsigned binary integer with a scaling factor.

VID codes used by INTEL microprocessor.

DIRECT format that uses an equation and the supplied coefficients.
Each Slave Device is required to support one type of data format for each command supported. Not all the
commands are required to be supported by PMBus systems, the command supported list should be determined
according to application needs.
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Implementation of PMBus Slave on XMC4500
2
Implementation of PMBus Slave on XMC4500
Implementation focuses on the robust communication functionality. Table 1 is a list of implemented commands
that are important to PMBus functionality.
Table 1
Commands Supported in the Slave Device
Code
Name
01h
OPERATION
03h
CLEAR_FAULTS
11h
12h
19h
20h
21h
3Ah
3Bh
STORE_DEFAULT_ALL
RESTORE_DEFAULT_ALL
CAPABILITY
VOUT_MODE
VOUT_COMMAND
FAN_CONFIG_1_2
FAN_COMMAND_1
55h
VIN_OV_FAULT_LIMIT
56h
VIN_OV_FAULT_RESPONSE
58h
VIN_UV_WARN_LIMIT
5Ah
VIN_UV_FAULT_RESPONSE
Application Guide
Packet
R/W
Byte
Data Format
Description
Specification
defined data format
Turn the Slave Device on/off
with control signal, and set the
output voltage to margins.
No, write only
Clear any fault bits set in the
status registers.
No, write only
Copy the entire contents of the
operating memory to the
matching locations in the nonvolatile Default Store memory.
No, write only
Copy the entire contents of the
non-volatile
Default
Store
memory to the matching
locations in the operating
memory.
Send
Byte
Send
Byte
Send
Byte
Specification
defined
Read
Byte
data format*
Specification
defined
R/W
Byte
data format*
LINEAR
R/W
Word
(output voltage
related)
R/W
Specification
defined
Byte
data format*
R/W
Word
R/W
Word
Byte
Word
R/W
Byte
12
Set the Slave Device output
voltage.
Configure up to two fans
associated with one PMBus
Slave Device.
Adjust the operation of the fan.
LINEAR
Set the VIN overvoltage value
The VIN overvoltage fault is
reported if the input voltage is
above this value.
data format*
R/W
Set or read the format of the
output voltage data.
LINEAR
Specification
defined
R/W
For Host system to determine
some key capabilities of a
PMBus Slave device.
Instruct the Slave on the action
to take in response to an input
overvoltage fault.
LINEAR
Set the VIN under voltage value
warning limit.
Specification
defined
Instruct the device on what
action to take in response to an
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Implementation of PMBus Slave on XMC4500
Code
Name
Packet
Data Format
data format*
78h
R/W
STATUS_BYTE
79h
STATUS_WORD
7Ch
STATUS_INPUT
Byte
R/W
Word
R/W
Byte
R/W
7Eh
STATUS_CML
81h
STATUS_FAN_1_2
88h
READ_VIN
8Bh
READ_VOUT
8Dh
READ_TEMPERATURE_1
Byte
R/W
Byte
Specification
defined data format*
Slave Device to return one byte
of information with a summary
of the most critical faults.
Specification
defined data format*
Slave Device to return two
bytes of information with a
summary of the Slave Device’s
fault condition.
Specification
defined data format*
Slave Device to return one byte
of information with input related
faults.
Specification
defined data format*
Slave Device to return one byte
of
information
with
communication,
logic
and
memory related faults.
Specification
defined data format*
Slave Device to report on the
status of any fans installed in
position 1 or position 2.
LINEAR
Slave Device to return the input
voltage.
LINEAR (output
voltage related)
Slave Device to return the
actual,
measured
(not
commanded) output voltage.
LINEAR
Slave Device to return the
measured
temperature
in
degree Celsius.
Read
Word
Read
Word
Description
input under voltage fault.
Read
Word
*Please refer to the PMBus Power System Management Protocol Specification, Part II, for the detailed data
format defined.
In this solution;

The CONTROL line and the SMALERT# signal are not implemented

The linear data format is used

Linear 11 data format is used for general parameters

Linear 16 data format is used for output voltage related parameters
The data format should be chosen according to the application requirements.
The functions for direct data format conversion are implemented as API functions. The user can call these
functions to convert the data to/from direct format.
A Packet error checking function is supported. This is enabled or disabled in the configuration file, config.h.
2.1
Hardware
2
2
The PMBus is operated with the I C clock and the I C data lines.
The CPU board used is the XMC4500 General Purpose Hexagon board, CPU_45A-V2. The XMC4500 has the
2
USIC module which can support I C communication.
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2
Table 2
Possible I C Clock/Data hardware pin assignments in XMC4500
Clock SCL
Data SDA
P0.8
P1.5
P0.11
P0.5 / P2.14
P1.1
P1.5
P2.4
P2.5 / P3.13
P3.0
P2.5 / P3.13
P5.8
P0.5 / P2.14
P6.2
P2.5 / P3.13
In this example;

P5.8 is used for I2C SCL

P2.14 is used for the I2C Data
2.2
Software
Here we describe the layers of functions in the software stack.
Figure 13
Software Layers
I2C Transport Layer
Implemented using the existing DAVE
TM
Apps.
Functions:

writes the value into the transmit buffer

reads the value from the receive buffer
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PMBus Protocol Layer
This layer configures the different protocols used by the PMBus commands. It configures the content and the
sequence of the data for the communication, and performs the communication fault check.
Application Layer
Here users can issue the command and configure the command data return.
For example, to read the input voltage of the Slave Device, the user can issue the command READ_VIN in
xSPY. This command is sent to the Host system:

The application layer of the Host system translates the command into PMBus protocol.

The protocol is translated into I C communication in the PMBus protocol layer.

The command is transmitted to the PMBus Slave Device through the I C transport layer.
2
2
On the Slave side, after receiving the command code from the Host:

The command code is translated to PMBus protocols. In this example, input voltage information is required
and the application layer will obtain the information in the system and pass the information to the PMBus
protocol layer.

The PMBus protocol layer configures the information into appropriate forms and passes it to the I C
transport layer.
2
2.2.1
Software Flow
Figure 14
PMBus Slave device, general software flow
Unlike the PMBus Host, the PMBus Slave is a passive device. It does not know when the Host will issue a
command, and cannot predict how the Host will behave. Therefore the operation depends on interrupt events.
The crucial interrupt events for the operation of the slave device are:

receive

repeated start

stop
The receive event of the command data starts the Slave operation.
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The command received from the Host is decoded into protocols. The system will then go in to a wait state to
wait for repeated start or stop conditions according to the protocol, read or write:

For write protocols, the Slave device only needs to receive the data from the Host (i.e. it does not need to
communicate back to the Host). Therefore the data is processed after the stop condition is received.

For read protocols, the Slave device needs to receive bytes from Host but also needs to communicate back
to the Host. Processing for the read protocol starts after the repeated start condition is received, which
signals the start of the read operation. After sending the required information to the Host, the Slave device
will wait for the Stop condition, which signals the end of communication session.
2.2.2
Software API Functions
2.2.2.1
PMBus Protocol Layer Interface API Functions
The functions defined in PMBUS001_DEVICE.c are for the PMBus protocol layer.
Table 3
PMBus Protocol Layer Interface API
API Functions Name
Description
void PMBusDevice(void)
Main function of PMBus device
void PMBusDevice_Init(void)
Initialization function for PMBus device before start operation
2.2.2.2
2
I C Transport Layer Interface API Functions
2
Two API functions are required to link the PMBus Protocol layer to the I C transport layer.
2
TM
The I C transport layer is covered by the DAVE
Table 4
App I2C003.
2
I C Transport Layer Interface API
API Functions Name
Description
Input Parameter
void IICSlaveTransmit(*data,
SendCount)
Configures the data for writing in to
the USIC FIFO
*data: address pointer to the data
that is to be transmitted
SendCount: number of data bytes to
be transmitted
void IICWriteData(*data)
Application Guide
Writes out a Word to the USIC FIFO
transmit buffer register without
waiting for any previous data to be
transmitted.
16
*data: address pointer to the data
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2.2.2.3
Data Storage API Functions
These API functions are used to store/retrieve PMBus data in the serial flash when memory access related
commands are received; For example, STORE_DEFAULT_ALL and RESTORE_DEFAULT_ALL commands.
The functions are defined in the MEMORYACCESS.c file.
If different flash memory is used to store the data, users will have to write their own functions to execute the
memory access commands.
Table 5
Data Storage API
API Functions Name
Description
void CmdRestoreDefaultAll(void)
Restore all PMBus parameters from Flash None
memory.
void CmdStoreDefaultAll(void)
Store all PMBus parameters to Flash
memory
None
Result EraseSector(void)
Erase the first sector of the SPI Serial
Flash.
Result = 1: Success
Program 256 bytes of data to the first
sector of the SPI Serial Flash
Result = 1: Success
Result ProgramPage(void)
2.2.2.4
Return Value
Result = 2: Erase Failed
Result = 2: Program Failed
Interrupt Handlers
The table lists the interrupt handlers used by the PMBus Slave device.
Table 6
Interrupt Handlers API
Handler Name
Description
Device_R_Start_stop_Handler()
Interrupt handler for protocol specific interrupt generated by device I C
system. The event defined is repeated start condition, stop condition and
slave read request event detected.
Device_Receive_Data_Handler()
Interrupt handler for FIFO standard receive buffer interrupt generated by
device USIC module FIFO system. The event defined is that data is
received from host system.
Device_Transmit_Data_Handler()
Interrupt handler for transmit shift interrupt generated by device USIC
module. The event defined is that data is transmitted out.
2.2.3
2
Packet Error Checking (PEC)
The PEC byte is used to ensure the data reliability of the communication. It is calculated with all the data byte in
the communication, including the Slave address and the read/write bit. The PEC uses an 8-bit cyclic
8
2
redundancy check (CRC-8). The polynomial used is C(x) = x + x + x + 1.
2.2.4
Fault Reporting Mechanism
When faults happen in the system, besides the default handling of the situation of the Slave, it will also use a
fault reporting mechanism to notify the Host. Reporting is via either:

SMBALERT

Host notify protocol
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SMBALERT requires an additional signal line connection between the Host and Slave Devices. In addition the
Host will need to send read status command with Alert Response Address to determine which Slave Device
pulled the alert line and the type of fault that has occurred.
Host notify protocol is used to save on hardware connection, and also to ease reporting procedures.
2.3
Implementation Consideration
When customizing the software stack for the dedicated application, the user must decide on the appropriate
adaptation to the code:

Based on the capability of the device on packet error checking, the value of PEC defined in CONFIG.h must
be changed accordingly:
− PEC = 0 will compile and build the project without packet error checking functionality.
− PEC = 1 will enable the function of packet error checking.

The suported PMBus commands are defined in the PMBUS001_DEVICE.h file. Users can choose the
relevant commands according to their application needs to form their own command set. The actions
performed in response to the commands (as described in the PMBus Specification) are not fully
implemented. Users need to alter the code according to their specific application. Users must provide the
correct data to send to the Host when requested and take appropriate actions in response to commands. If
new commands are required, the users will need to add the definition of the new commands to the
PMBUS001_DEVICE.h file. An update on the command list (PMBusCommand[]) in PMBUS001_DEVICE.c
file is also required.

The Slave address can be changed in CONFIG.h, in the defined value SlaveAddress. Note that the Slave
address is expressed in 7 bits.
2.3.1
How to modify a response for a command
All the commands defined in the system are editable. Users can add or change the actions according to their
application needs. If changes are needed, use the following steps:
1. Find the bus protocol of the command that needs to be edited.
2. Go to the PMBusDevice() function in the PMBUS001_DEVICE.c file. Find the marked space for user code to
be inserted.
3. Go to the space of the respective bus protocol (SendByte, WriteByte, etc) and the PMBus commands are
there in the form of switch cases. The actions to be defined can be put inside the command switch case. If
the command does not exist, a new switch case has to be added.
switch(mode)
{
Case SendByte:
…
// USER CODE for SendByte case BEGIN
…
// USER CODE for SendByte case END
Break;
…
}
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Implementation of PMBus Slave on XMC4500
2.3.2
How to add a command
It is possible to add other commands defined in the specification, but the response of the Slave device then
needs to be programmed by the user.
1. Find the number of the required command and determine the bus protocol of the new command.
2. Go to the PMBUS001_DEVICE.h file and add in the command definition for the new command
3. Go to the PMBUS001_DEVICE.c file and add the command number to the array PMBusCommand[],
according to the bus protocol.
4. Go to the function Device_CommandProtocolIdentify(), change ‘x’ in the compare check ‘CmdIndex < x’ to
the correct value.
5. Go to the function PMBusDevice() in the PMBUS001_DEVICE.c file, and add a new switch case inside the
user code space. This defines the response of the device to the command.
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Application example
3
Application example
Our example project uses potentiometer values to simulate input voltage values. The input voltage is set by
varying the potentiometer. If the input voltage exceeds the over-voltage limit, or falls below the under-voltage
limit, there will be an error condition and the Slave device will notify the Host via the host notify protocol.
3.1
Getting started
The example project provided is a simple PMBus system with one Host and one Slave device.
Figure 15
PMBus hardware connection
3.1.1
Hardware setup
Slave Hardware required
1. XMC4500 Hexagon CPU General Purpose Board, CPU_45A-V2
2. Pin Extension Board, UNI_EXT01-V2
3. J-Link Lite Debugger
Master Hardware required
1. XMC4400 Hexagon CPU General Purpose Board, CPU_44A-V2
2. Pin Extension Board, UNI_EXT01-V2
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Application example
Figure 16
Slave Board – XMC4500 Connection Guide
The hardware setup for the PMBus Slave Device:
1. Connect a 5V power to the XMC4500 board.
2. Connect the J-link debugger to the XMC4500 board to download the PMBus Slave code.
3. Remove the J-link debugger.
4. Connect to the PMBus using the pin extension board on the COM side. There are two signal lines: SCL
(clock) and SDA (data).
Figure 17
Master Board – XMC4400 Connection Guide
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Application example
The hardware setup for the PMBus Host (Master):
1. Connect a 5V power to the XMC4400 board.
2. Connect a mini USB cable to the XMC4400 board to download the PMBus Host code. The same connection
is used for xSPY communication to the laptop.
3. Connect to the PMBus using the pin extension board on the COM side. There are two signal lines: SCL
(clock) and SDA (data).
Note: Ensure that there is a common ground between the Host and Slave Device for this setup.
3.2
XMC4500 PMBus Software Package for Slave Device
Table 7
List of DAVE
TM
Apps used
Apps
Description
ADC002
Configure an ADC kernel for the VIN measurement
CLK001
Configure the system and peripheral clocks
DAVESupport
DAVE
I2C003
Configure one of the USIC channels as I C Slave
NVIC002
Interrupt handler apps
PWMSP001
Use as a timer to trigger ADC conversion
RESET001
Provides API to assert/de-assert peripheral modules
SPI001
Configure one of the USIC channels as SPI.
TM
Apps initialization and configure the multiplexer registers
2
This is used to communicate with the Serial Flash memory.
Table 8
List of source files (excluding DAVE
TM
generated files)
Filename
Description
Main.c
The main tasks of this example project.
MEMORYACCESS.c
Functions that handle the PMBus memory access commands and trigger memory
read, program or erase the PMBus parameter in the Serial Flash memory.
PMBUS001_DEVICE.c
PMBus protocol layer functions implementation.
PMBUS001_GENERAL.c
Functions related to data conversions and packet error checking.
S25FL032P.c
Handles the commands required to communicate to the Serial Flash memory
CONFIG.h
Configuration of the supported features.
MEMORYACCESS.h
Function declarations that are defined in MEMORYACCESS.c.
PMBUS001_DEVICE.h
PMBus command definitions and the PMBus protocol layer function declarations.
PMBUS001_GENERAL.h
Function declarations that are defined in PMBUS001_GENERAL.c.
S25FL032P.h
Function declarations that are defined in S25FL032P.c
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Conclusion
4
Conclusion
Today we see a shift towards digital based solutions in power conversion technology and this requires a
communication capability in the power system. The PMBus facilitates communication with power converters and
other devices in the power system and therefore addresses this need.
The XMC4000 microcontroller provides the PMBus protocol with its powerful USIC module, and the PMBus
protocol software has been developed in accordance with the PMBus Standard.
From the application example given, users are able to customize and configure the PMBus protocol software to
their own power system.
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References
5
References
[1]
XMC4500 Reference Manual, version 1.2, December 2012
[2]
PMBus Power System Management Protocol Specification, revision 1.2, September 2010
[3]
Power Management Bus Implementer’s Forum, PMBus™: The Power System Standard
[4]
System Management Interface Forum, System Management Interface Forum (SMIF)
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w w w . i n f i n e o n . c o m
Published by Infineon Technologies AG
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