STMicroelectronics STM32F405 User Manual

DocID018909 Rev 11 845/1731
RM0090 Inter-integrated circuit (I
2
C) interface
864
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/).
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/).
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 122. 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

STMicroelectronics STM32F405 Specifications

General

Brand	STMicroelectronics
Model	STM32F405
Category	Controller
Language	English