IDT 89HPES24N3A, User Manual

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IDT SMBus Interfaces
PES24N3A User Manual 6 - 12 April 10, 2008
Notes
Figure 6.5 Slave SMBus Command Code Format
The FUNCTION field in the command code indicates if the SMBus operation is a CSR register read/
write or a serial EEPROM read/write operation. Since the format of these transactions is different, each will
be described in the following sections. If a command is issued while one is already in progress or if the
slave is unable to supply data associated with a command, the command is NACKed. This indicates to the
master that the transaction should be retried.
CSR Register Read or Write Operation
Table 6.10 indicates the sequence of data as it is presented on the slave SMBus following the byte
address of the Slave SMBus interface.
Bit Name Description
0 END End of transaction indicator. Setting both START and END
signifies a single transaction sequence.
0 - Current transaction is not the last read or write
sequence.
1 - Current transaction is the last read or write sequence.
1 START Start of transaction indicator. Setting both START and END
signifies a single transaction sequence.
0 - Current transaction is not the first of a read or write
sequence.
1 - Current transaction is the first of a read or write
sequence.
4:2 FUNCTION This field encodes the type of SMBus operation.
0 - CSR register read or write operation
1 - Serial EEPROM read or write operation
2 through 7 - Reserved
6:5 SIZE This field encodes the data size of the SMBus transaction.
0 - Byte
1 - Word
2 - Block
3 - Reserved
7 PEC This bit controls whether packet error checking is enabled
for the current SMBus transaction.
0 - Packet error checking disabled for the current SMBus
transaction.
1 - Packet error checking enabled for the current SMBus
transaction.
Table 6.9 Slave SMBus Command Code Fields
Bit
6
Bit
7
Bit
0
Bit
1
Bit
2
Bit
3
Bit
4
Bit
5
END START FUNCTION SIZE PEC