Hello Here is the format of the bus transaction http://www.reed-electronics.com/ednmag/filtered/pdfs/contents/images/333665fa.pdf Some article about thermal management in PC and about buses it uses. http://www.reed-electronics.com/ednmag/article/CA339714 Here is what is relevant: SensorPath offloads traffic from the SMBus onto a single-wire digital bus that's controlled by a dedicated I/O chip. The scheme accommodates as many as seven devices per bus, each of which can accommodate three functions. As well as temperature sensing, possible functions include system-voltage sensing (with or without core-voltage support) and support for EEPROM devices. Uwe Kopp, National Semiconductor's European marketing manager for its data-conversion-systems group, explains that in common with SMBus, SensorPath employs master/slave architecture; however, SensorPath masters exchange data with slaves using an unusual pulse-width-coding scheme. A "0" data bit is the shortest at 11.8 to 17.0 usec, and a "1" occupies 30.7 to 42.5 usec. A "start" bit is 63.7 to 87 usec long, attention requests take 130 to 180 usec and reset is the longest pulse at 236 to 370 usec. Thus, the minimum tolerance for the 360-kHz reference oscillator is more than 15% to allow for low-cost oscillators. The maximum operating frequency of 100 kHz retains compatibility with SMBus. The data-exchange protocol is simple, with the master initiating a transfer with a start bit and device number, followed by a data field. Slaves respond with an acknowledge signal and can also signal the master via an attention sequence (Figure A). A minimum bus-inactive period of 7.1 usec separates data exchanges. Each device on the bus senses attention requests, which allows the protocol to negotiate and regain control in case of bus contention. Both masters and slaves can force a reset; hence, a single wire accommodates all data-transfer requirements. Devices can use hard-wired addresses to save register space and die area, or respond to programmable addresses that the master issues. In each case, the master has to send an appropriate address to talk to a device. Regards Rudolf
