307013-003 Datasheet, PDF (221/848 Pages) Intel Corporation – Intel I/O Controller Hub 7

Functional Description
Note:
Note:
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. See section 5.5.4 of the System Management Bus
(SMBus) Specification, Version 2.0 for the format of the protocol.
Read Byte/Word
Reading data is slightly more complicated than writing data. First the ICH7 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. See section 5.5.5 of the System
Management Bus (SMBus) Specification, Version 2.0 for the format of the protocol.
Process Call
The process call is so named because a command sends data and waits for the slave to
return a value dependent on that data. The protocol is simply a Write Word followed by
a Read Word, but without a second command or stop condition.
When programmed for the Process Call command, the ICH7 transmits the Transmit
Slave Address, Host Command, DATA0 and DATA1 registers. Data received from the
device is stored in the DATA0 and DATA1 registers. The Process Call command with
I2C_EN set and the PEC_EN bit set produces undefined results. Software must force
either I2C_EN or PEC_EN to 0 when running this command. See section 5.5.6 of the
System Management Bus (SMBus) Specification, Version 2.0 for the format of the
protocol.
For process call command, the value written into bit 0 of the Transmit Slave Address
Register (SMB I/O register, offset 04h) needs to be 0.
If the I2C_EN bit is set, the protocol sequence changes slightly: the Command Code
(bits 18:11 in the bit sequence) are not sent - as a result, the slave will not
acknowledge (bit 19 in the sequence).
Block Read/Write
The ICH7 contains a 32-byte buffer for read and write data which can be enabled by
setting bit 1 of the Auxiliary Control register at offset 0Dh in I/O space, as opposed to a
single byte of buffering. This 32-byte buffer is filled with write data before
transmission, and filled with read data on reception. In the ICH7, the interrupt is
generated only after a transmission or reception of 32 bytes, or when the entire byte
count has been transmitted/received.
The byte count field is transmitted but ignored by the ICH7 as software will end the
transfer after all bytes it cares about have been sent or received.
For a Block Write, software must either force the I2C_EN bit or both the PEC_EN and
AAC bits to 0 when running this command.
Intel ^® ICH7 Family Datasheet
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