IDT SMBus Interfaces
PES48T12G2 User Manual
12 - 16
April 5, 2013
Notes
Serial EEPROM Read or Write Operation
Table 12.15 indicates the sequence of data as it is presented on the slave SMBus following the byte
address of the Slave SMBus interface.
Bit
Field
Name
Type
Description
0
BELL
Read/Write
Byte Enable Lower
. When set, the byte enable for bits [7:0] of the
data word is enabled.
1
BELM
Read/Write
Byte Enable Lower Middle
. When set, the byte enable for bits [15:8]
of the data word is enabled.
2
BEUM
Read/Write
Byte Enable Upper Middle
. When set, the byte enable for bits
[23:16] of the data word is enabled.
3
BEUU
Read/Write
Byte Enable Upper.
When set, the byte enable for bits [31:24] of the
data word is enabled.
4
OP
Read/Write
CSR Operation. This field encodes the CSR operation to be per-
formed.
0 - CSR write
1 - CSR read
5
0
0
Reserved.
Must be zero
6
RERR
1
1.
The RERR and WERR bits are driven by the switch as status bits that indicate whether or not the switch’s SMBus slave in-
terface accepted the register read/write command (the switch accepts the access if it has the correct byte sequence). When a
byte sequence refers to a register offset that is not listed or is regarded as a reserve register, the RERR and WERR bits will be
set after a read or write operation is performed.
Read-Only
and Clear
Read Error
. This bit is set if the last CSR read SMBus transaction
was not claimed by the device. Success indicates that the transaction
was claimed, not necessarily that the operation completed without
error.
7
WERR
Read-Only
and Clear
Write Error
. This bit is set if the last CSR write SMBus transaction
was not claimed by the device. Success indicates that the transaction
was claimed, not necessarily that the operation completed without
error.
Table 12.14 CSR Register Read or Write CMD Field Description
Byte
Position
Field
Name
Description
0
CCODE
Command Code.
Slave Command Code field described in Table
1
BYTCNT
Byte Count.
The byte count field is only transmitted for block type
SMBus transactions. SMBus word and byte accesses to not contain
this field. The byte count field indicates the number of bytes following
the byte count field when performing a write or setting up for a read.
The byte count field is also used when returning data to indicate the
number of following bytes (including status).
2
CMD
Command.
This field contains information related to the serial
EEPROM transaction
Table 12.15 Serial EEPROM Read or Write Operation Byte Sequence (Part 1 of 2)
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