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IDT SMBus Interfaces
PES24T3G2 User Manual
5 - 14
February 22, 2012
Notes
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. They will
be described individually 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 indi-
cates to the master that the transaction should be retried.
CSR Register Read or Write Operation
Table 5.11 indicates the sequence of data as it is presented on the slave SMBus following the byte
address of the Slave SMBus interface.
Table 5.11 indicates the sequence of data as it is presented on the slave SMBus following the byte
address of the Slave SMBus interface. Dword addresses and not byte addresses must be used to access
all visible software registers. ADDRL and ADDUL represent the lower 8-bit of the doubleword system
4:2
FUNC-
TION
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 cur-
rent SMBus transaction.
0 - Packet error checking disabled for the current SMBus transaction.
1 - Packet error checking enabled for the current SMBus transaction.
Byte
Position
Field
Name
Description
0
CCODE
Command Code. Slave Command Code field described in Table 5.10.
1
BYTCNT
Byte Count. The byte count field is only transmitted for block type SMBus transac-
tions. SMBus word and byte accesses do 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 indi-
cate 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 opera-
tion.
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 system 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 5.11 CSR Register Read or Write Operation Byte Sequence
Bit
Field
Name
Description
Table 5.10 Slave SMBus Command Code Fields (Part 2 of 2)
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Страница 16: ...IDT List of Figures PES24T3G2 User Manual viii February 22 2012 Notes...
Страница 20: ...IDT Register List PES24T3G2 User Manual xii February 22 2012 Notes...
Страница 32: ...IDT PES24T3G2 Device Overview PES24T3G2 User Manual 1 12 February 22 2012 Notes...
Страница 72: ...IDT SMBus Interfaces PES24T3G2 User Manual 5 20 February 22 2012 Notes...
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