ST STM32F40 Series User Manual

RM0090 Inter-integrated circuit (I
2
C) interface
Doc ID 018909 Rev 4 722/1422
Differences between SMBus and I
2
C
The following table describes the differences between SMBus and I
2
C.
SMBus application usage
With System Management Bus, a device can provide manufacturer information, tell the
system what its model/part number is, save its state for a suspend event, report different
types of errors, accept control parameters, and return its status. SMBus provides a control
bus for system and power management related tasks.
Device identification
Any device that exists on the System Management Bus as a slave has a unique address
called the Slave Address. For the list of reserved slave addresses, refer to the SMBus
specification version. 2.0 (http://smbus.org/specs/).
Bus protocols
The SMBus specification supports up to 9 bus protocols. For more details of these protocols
and SMBus address types, refer to SMBus specification version. 2.0
(http://smbus.org/specs/). These protocols should be implemented by the user software.
Address resolution protocol (ARP)
SMBus slave address conflicts can be resolved by dynamically assigning a new unique
address to each slave device. The Address Resolution Protocol (ARP) has the following
attributes:
● Address assignment uses the standard SMBus physical layer arbitration mechanism
● Assigned addresses remain constant while device power is applied; address retention
through device power loss is also allowed
● No additional SMBus packet overhead is incurred after address assignment. (i.e.
subsequent accesses to assigned slave addresses have the same overhead as
accesses to fixed address devices.)
● Any SMBus master can enumerate the bus
Unique device identifier (UDID)
In order to provide a mechanism to isolate each device for the purpose of address
assignment, each device must implement a unique device identifier (UDID).
Table 104. SMBus vs. I
2
C
SMBus I
2
C
Max. speed 100 kHz Max. speed 400 kHz
Min. clock speed 10 kHz No minimum clock speed
35 ms clock low timeout No timeout
Logic levels are fixed Logic levels are V
DD
dependent
Different address types (reserved, dynamic etc.) 7-bit, 10-bit and general call slave address types
Different bus protocols (quick command, process
call etc.)
No bus protocols

ST STM32F40 Series Specifications

General

Brand	ST
Model	STM32F40 Series
Category	Microcontrollers
Language	English