82801DB Datasheet, PDF (213/587 Pages) Intel Corporation – Intel 82801DB I/O Controller Hub 4 (ICH4)

Functional Description
Table 5-82. 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
Read Byte/Word
Reading data is slightly more complicated than writing data. First the ICH4 must write a command
to the slave device. Then it must follow that command with a repeated start condition to denote a
read from that device’s address. The slave then returns 1 or 2 bytes of data. Software must force the
I2C_EN bit to 0 when running this command.
When programmed for the read byte/word command, the Transmit Slave Address and Device
Command Registers are sent. Data is received into the DATA0 on the read byte, and the DAT0 and
DATA1 registers on the read word. The format of the protocol is shown in Table 5-83 and
Table 5-84.
Intel^® 82801DB ICH4 Datasheet
213