82801FB Datasheet, PDF (217/786 Pages) Intel Corporation – Intel I/O Controller Hub 6 (ICH6) Family

Functional Description
message. Also, the Block Write protocol sequence changes slightly: the Byte Count (bits 27:20 in
the bit sequence) are not sent - as a result, the slave will not acknowledge (bit 28 in the sequence).
I²C Read
This command allows the ICH6 to perform block reads to certain I²C devices, such as serial
E²PROMs. The SMBus Block Read supports the 7-bit addressing mode only.
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.
For I²C Read command, the value written into bit 0 of the Transmit Slave Address Register (SMB
I/O register, offset 04h) needs to be 0.
The format that is used for the command is shown in Table 5-47.
Table 5-47. I²C Block Read
Bit
Description
1 Start
8:2 Slave Address — 7 bits
9 Write
10 Acknowledge from slave
18:11 Send DATA1 register
19 Acknowledge from slave
20 Repeated Start
27:21 Slave Address — 7 bits
28 Read
29 Acknowledge from slave
37:30 Data byte 1 from slave — 8 bits
38 Acknowledge
46:39 Data byte 2 from slave — 8 bits
47 Acknowledge
– Data bytes from slave / Acknowledge
– Data byte N from slave — 8 bits
– NOT Acknowledge
– Stop
The ICH6 will continue reading data from the peripheral until the NAK is received.
Intel^® I/O Controller Hub 6 (ICH6) Family Datasheet
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