82801DB Datasheet, PDF (212/587 Pages) Intel Corporation – Intel 82801DB I/O Controller Hub 4 (ICH4)

Functional Description
Table 5-80. Send/Receive Byte Protocol with PEC
Send 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
PEC
Acknowledge from slave
Stop
Bit
1
2–8
9
10
11–18
19
20–27
28
29
Receive Byte Protocol
Description
Start
Slave Address - 7 bits
Read
Acknowledge from slave
Data byte from slave
Acknowledge
PEC from slave
Not Acknowledge
Stop
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 Data0 Registers are sent. In addition, the Data1 Register is sent on a Write
Word command. Software must force the I2C_EN bit to 0 when running this command. The format
of the protocol is shown in Table 5-81 and Table 5-82.
Table 5-81. 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
212
Intel^® 82801DB ICH4 Datasheet