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IDT SMBus Interfaces
PES24N3A User Manual 6 - 13 April 10, 2008
Notes
The format of the CMD field is shown in Figure 6.6 and described in Table 6.11.
Figure 6.6 CSR Register Read or Write CMD Field Format
Byte
Position
Field Name Description
0 CCODE Command Code. Slave Command Code field described in
Table 6.9.
1 BYTCNT Byte Count. The byte count field is only transmitted for
block type SMBus transactions. SMBus word and byte
accesses do not contain this field. The byte count field indi-
cates 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).
Note that the
byte count field does not include the PEC byte if PEC is
enabled.
2 CMD Command. This field encodes fields related to the CSR
register read or write operation.
3 ADDRL Address Low. Lower 8-bits of the doubleword CSR system
address of register to access.
4 ADDRU Address Upper. Upper 6-bits of the doubleword CSR sys-
tem address of register to access. Bits 6 and 7 in the byte
must be zero and are ignored by the hardware.
5 DATALL Data Lower. Bits [7:0] of data doubleword.
6 DATALM Data Lower Middle. Bits [15:8] of data doubleword.
7 DATAUM Data Upper Middle. Bits [23:16] of data doubleword.
8 DATAUU Data Upper. Bits [31:24] of data doubleword.
Table 6.10 CSR Register Read or Write Operation Byte Sequence
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.
Table 6.11 CSR Register Read or Write CMD Field Description (Part 1 of 2)
Bit
6
Bit
7
Bit
0
Bit
1
Bit
2
Bit
3
Bit
4
Bit
5
BELL BELM WERR BEUM BEUU OP RERR 0