Functional Description
218 Datasheet
I
2
C Read
This command allows the PCH to perform block reads to certain I
2
C devices, such as
serial E
2
PROMs. The SMBus Block Read supports the 7-bit addressing mode only.
However, this does not allow access to devices using the I
2
C “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 I
2
C 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 I
2
C 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 5-44.
The PCH will continue reading data from the peripheral until the NAK is received.
Table 5-44. I
2
C Block Read
Bit Description
1Start
8:2 Slave Address – 7 bits
9Write
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
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