82801BA Datasheet, PDF (195/498 Pages) Intel Corporation – Intel 82801BA I/O Controller Hub 2 (ICH2) and Intel 82801BAM I/O Controller Hub 2 Mobile

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 ICH2 transmits the Transmit Slave Address,
Host Command, DATA0 and DATA1 registers. Data received from the device is stored in the
DATA0 and DATA1 registers. The format of the protocol is shown in Table 5-80.
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 5-80. Process Call Protocol
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
Acknowledge from slave
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
82801BA ICH2 and 82801BAM ICH2-M Datasheet
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