82801CA Datasheet, PDF (197/521 Pages) Intel Corporation – I/O Controller Hub 3-S (ICH3-S)

Functional Description
Write Byte/Word
The first byte of a Write Byte/Word access is the command code. The next 1 or 2 bytes are the data
to be written. When programmed for a Write Byte/Word command, the transmit slave address,
device command, and Data 0 Registers are sent. In addition, the Data 1 Register is sent on a Write
Word command. The Write Byte / Word command with I2C_EN set produces undefined results.
Software should force the I2C_EN bit to 0 when running this command. The format of the protocol
is shown in Table 5-80 and Table 5-81.
Table 5-80. Write Byte/Word Protocol without PEC
Write Byte Protocol
Bit
1
2–8
9
10
11–18
19
20–27
28
29
Description
Start
Slave Address–7 bits
Write
Acknowledge from slave
Command code–8 bits
Acknowledge from slave
Data Byte–8 bits
Acknowledge from Slave
Stop
Bit
1
2–8
9
10
11–18
19
20–27
28
29–36
37
38
Write Word Protocol
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
Stop
Table 5-81. Write Byte/Word Protocol with PEC
Write Byte Protocol
Bit
1
2–8
9
10
11–18
19
20–27
28
29–36
37
38
Description
Start
Slave Address–7 bits
Write
Acknowledge from slave
Command code–8 bits
Acknowledge from slave
Data Byte–8 bits
Acknowledge from Slave
PEC
Acknowledge from Slave
Stop
Bit
1
2–8
9
10
11–18
19
20–27
28
29–36
37
38–45
46
47
Write Word Protocol
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
PEC
Acknowledge from slave
Stop
Intel^® 82801CA ICH3-S Datasheet
197