82801DB Datasheet, PDF (218/587 Pages) Intel Corporation – Intel 82801DB I/O Controller Hub 4 (ICH4)

Functional Description
Table 5-88. Block Read/Write Protocol with PEC
Block Write Protocol
Bit
1
2–8
9
10
11–18
19
20–27
28
29–36
37
38–45
46
...
...
...
...
...
...
Description
Start
Slave Address - 7 bits
Write
Acknowledge from slave
Command code - 8 bits
Acknowledge from slave
Byte Count - 8 bits
(Skip this step if I2C_EN bit set)
Acknowledge from Slave
(Skip this step if I2C_EN bit set)
Data Byte 1 - 8 bits
Acknowledge from Slave
Data Byte 2 - 8 bits
Acknowledge from slave
Data Bytes / Slave
Acknowledges...
Data Byte N - 8 bits
Acknowledge from Slave
PEC - 8 bits
Acknowledge from Slave
Stop
Bit
1
2–8
9
10
11–18
19
Block Read Protocol
Description
Start
Slave Address - 7 bits
Write
Acknowledge from slave
Command code - 8 bits
Acknowledge from slave
20
Repeated Start
21–27 Slave Address - 7 bits
28
29
30–37
38
Read
Acknowledge from slave
Byte Count from slave - 8 bits
Acknowledge
39–46 Data Byte 1 from slave - 8 bits
47
48–55
56
...
...
...
...
...
...
Acknowledge
Data Byte 2 from slave - 8 bits
Acknowledge
Data Bytes from slave/Acknowledge
Data Byte N from slave - 8 bits
Acknowledge
PEC from slave - 8 bits
NOT Acknowledge
Stop
I²C Read
This command allows the ICH4 to perform block reads to certain I²C devices (e.g., serial
E²PROMs) in 10-bit addressing mode only. The SMBus Block Read sends both the 7-bit address,
as well as the Command field. This command field could be used as the extended 10-bit address for
accessing I²C devices that use 10-bit addressing.
However, this does not allow access to devices using the I²C “Combined Format” that has data
bytes after the address. Typically these data bytes correspond to an offset (address) within the serial
memory chips.
Note: This command is supported independent of the setting of the I2C_EN bit. The I²C Read command
with the PEC_EN bit set produces undefined results. Software must force both the PEC_EN and
AAC bit to 0 when running this command.
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Intel^® 82801DB ICH4 Datasheet