Title: SMBus
Description:
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 . SMBus provides a control bus for system and power management related tasks. A system may use SMBus to pass messages to and from devices instead of tripping individual control lines. Removing the individual control lines reduces pin count. Accepting messages ensures future expandability. 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.The System Management Bus Specification refers to three types of devices. A slave is a device that is receiving or responding to a command. A master is a device that issues commands, generates the clocks, and terminates the transfer. A host is a specialized master that provides the main interface to the system's CPU. A host must be a master-slave and must support the SMBus host notify protocol. There may be at most one host in a system. One example of a hostless system is a simple battery charging station. The station might sit plugged into a wall waiting to charge a smart battery. A device may be designed so that it is never a master and always a slave. A device may act as a slave most of the time, but in special instances it may become a master. A device can also be designed to be a master only. A system host is an example of a device that acts as a host most of the time but that includes some slave behavior..
Any device that exists on the System Management Bus as a slave has a unique address called the Slave Address. For reference, the following addresses are reserved and must not be used by or assigned to any SMBus slave device unless otherwise detailed by this specification.
Bits 7-1:Slave Address
Bit 0: R/W# bit
Addr RW Comment
0000 000 0 General Call Address
0000 000 1 START byte
0000 001 X CBUS address
0000 010 X Address reserved for different bus format
0000 011 X Reserved for future use
0000 1XX X Reserved for future use
0101 000 X Reserved for ACCESS.bus host
0110 111 X Reserved for ACCESS.bus default address
1111 0XX X 10-bit slave addressing
1111 1XX X Reserved for future use
0001 000 X SMBus Host
0001 100 X SMBus Alert Response Address
1100 001 X SMBus Device Default Address
All other addresses are available for address assignment for dynamic address devices and/or for miscellaneous devices. Miscellaneous device addresses are discussed in Section 5.2.1.4.
Licence: GNU LGPL
@author Francois-Frederic Ozog @version 1.0
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