GD32F10x User Manual
470
17.3.11.
SMBus support
The System Management Bus (abbreviated to SMBus or SMB) is a single-ended simple two-
wire bus for the purpose of lightweight communication. Most commonly it is found in computer
motherboards for communication with power source for ON/OFF instructions.It is derived from
I2C for communication with low-bandwidth devices on a motherboard, especially power
related chips such as a laptop's rechargeable battery subsystem (see Smart Battery Data).
SMBus protocol
Each message transmission on SMBus follows the format of one of the defined SMBus
protocols. The SMBus protocols are a subset of the data transfer formats defined in the I2C
specifications. I2C devices that can be accessed through one of the SMBus protocols are
compatible with the SMBus specifications. I2C devices that do not adhere to these protocols
cannot be accessed by standard methods as defined in the SMBus and Advanced
Configuration and Power Management Interface (abbreviated to ACPI) specifications.
Address resolution protocol
The SMBus is realized based on I2C hardware and it uses I2C hardware addressing, but it
adds the second-level software for building special systems. Additionally, its specifications
include an Address Resolution Protocol that can make dynamic address allocations. Dynamic
reconfiguration of the hardware and software allows bus devices to be ‘hot-plugged’ and used
immediately, without restarting the system. The devices are recognized automatically and
assigned unique addresses. This advantage results in a plug-and-play user interface. In this
protocol there is a very useful distinction between a system host and all the other devices in
the system, that is the host provides address assignment function.
Time-out feature
SMBus has a time-out feature which resets devices if a communication takes too long. This
explains the minimum clock frequency is 10 kHz to prevent locking up the bus. I2C can be a
‘DC’ bus, which means that a slave device stretches the master clock when performing some
routines while the master is accessing it. This will notify the master that the slave is busy but
does not want to lose the communication. The slave device will continue the communication
after its task is completed. There is no limit in the I2C bus protocol of how long this delay can
be, whereas for a SMBus system, it would be limited to 35ms. SMBus protocol just assumes
that if something takes too long, then it means that there is a problem on the bus and that all
devices must reset in order to solve the problem. Slave devices are not allowed to hold the
clock low too long.
Packet error checking
SMBus 2.0 and 1.1 allow Packet Error Checking (PEC). In that mode, a PEC byte is appended
at the end of each transaction. The byte is a CRC-8 checksum of the entire message including
Summary of Contents for GD32F10 Series
Page 63: ...GD32F10x User Manual 63 programmed during the chip production ...
Page 117: ...GD32F10x User Manual 117 010 1 0 011 0 9 ...
Page 416: ...GD32F10x User Manual 416 shadow register updates every update event ...
Page 427: ...GD32F10x User Manual 427 value ...
Page 518: ...GD32F10x User Manual 518 These bits are not used in SPI mode ...