82801CA Datasheet, PDF (209/521 Pages) Intel Corporation – I/O Controller Hub 3-S (ICH3-S)

Functional Description
5.17.6.2 Format of Read Command
The external master performs Byte Read commands to the ICH3 SMBus Slave I/F. The
“Command” field (bits 11–18) indicate which register is being accessed. The Data field
(bits 30–37) contain the value that should be read from that register.
Table 5-94 shows the Read Cycle format. Table 5-95 shows the register mapping for the data byte.
Table 5-94. Read Cycle Format
Bit
Description
1 Start
2–8 Slave Address–7 bits
9 Write
10 ACK
11–18 Command code – 8 bits
19 ACK
20 Repeated Start
21–27 Slave Address–7 bits
28 Read
29 ACK
30–37 Data Byte
38 NOT ACK
39 Stop
Driven By
Comment
External Microcontroller
External Microcontroller
Must match value in Receive Slave Address
Register
External Microcontroller Always 0
ICH3
External Microcontroller
Indicates which register is being accessed.
See Table 5-95.
ICH3
External Microcontroller
External Microcontroller
Must match value in Receive Slave Address
Register
External Microcontroller Always 1
ICH3
ICH3
Value depends on register being accessed.
See Table 5-95.
External Microcontroller
External Microcontroller
Intel^® 82801CA ICH3-S Datasheet
209