82801CA Datasheet, PDF (200/521 Pages) Intel Corporation – I/O Controller Hub 3-S (ICH3-S)

Functional Description
Process Call
The process call is so named because a command sends data and waits for the slave to return a
value dependent on that data. The protocol is simply a Write Word followed by a Read Word, but
without a second command or stop condition.
When programmed for the Process Call command, the ICH3 transmits the Transmit Slave Address,
Host Command, Data 0, and Data 1 Registers. Data received from the device is stored in the Data 0
and Data 1 Registers. The Process Call command with I2C_EN set and the PEC_EN bit set
produces undefined results. Software must force either I2C_EN or PEC_EN to 0 when running this
command. The format of the protocol is shown in Table 5-84 and Table 5-85.
Note: For Process Call command, the value written into bit 0 of the Transmit Slave Address Register
(SMB I/O Register, offset 04h) needs to be 0.
Table 5-84. Process Call Protocol without PEC
Bit
1
2–8
9
10
11–18
19
20–27
28
29–36
37
38
39–45
46
47
48–55
56
57–64
65
66
Description
Start
Slave Address–7 bits
Write
Acknowledge from Slave
Command code–8 bits (skip this step if I2C_EN bit
is set)
Acknowledge from slave (skip this step if I2C_EN
bit is set)
Data byte Low–8 bits
Acknowledge from slave
Data Byte High–8 bits
Acknowledge from slave
Repeated Start
Slave Address–7 bits
Read
Acknowledge from slave
Data Byte Low from slave–8 bits
Acknowledge
Data Byte High from slave–8 bits
NOT acknowledge
Stop
200
Intel^® 82801CA ICH3-S Datasheet