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IDT SMBus Interfaces
Notes
PES4T4 User Manual
Byte 0
Byte 1
Byte 2
Byte 3
Byte 4
Byte 5
Byte 6
Byte 7
Byte 4n+4
Byte 4n+ 5
Byte 4n+6
Byte 4n+7
Figure 6.2 Sequential Double Word Initialization Sequence Format
The final type of configuration block is the configuration done sequence which is used to signify the end
of a serial EEPROM initialization sequence. If during serial EEPROM initialization, an attempt is made to
initialize a register that is not defined in a configuration space (i.e., not defined in Chapter 9, Configuration
Registers), then the Unmapped Register Initialization Attempt (URIA) bit is set in the SMBUSSTS register
and the write is ignored.
The configuration done sequence consists of two fields and its format is shown in Figure 6.2. The
CHECKSUM field contains the checksum of all of the bytes in all of the fields read from the serial EEPROM
from the first configuration block to the end of this done sequence. The second field is the TYPE field which
is always 0x3 for configuration done sequences.
Byte 0
Byte 1
Figure 6.3 Configuration Done Sequence Format
The checksum in the configuration done sequence enables the integrity of the serial EEPROM initializa-
tion to be verified. Since uninitialized EEPROMs typically have a value of all ones, initialization from an
uninitialized serial EEPROM will result in a checksum mismatch. The checksum is computed in the
following manner. An 8-bit counter is initialized to zero and the 8-bit sum is computed over the configuration
bytes stored in the serial EEPROM, including the entire contents of the configuration done sequence, with
the checksum field initialized to zero.
1.
This includes the byte containing the TYPE field.
Bit
Bit
Bit
Bit
Bit
Bit
7
6
5
4
3
CSR_SYSADDR[7:0]
TYPE
CSR_SYSADDR[13:8]
0x1
NUMDW[7:0]
NUMDW[15:8]
DATA0[7:0]
DATA0[15:8]
DATA0[23:16]
DATA0[31:24]
DATAn[7:0]
DATAn[15:8]
DATAn[23:16]
DATAn[31:24]
Bit
Bit
Bit
Bit
Bit
Bit
7
6
5
4
3
CHECKSUM[7:0]
TYPE
Reserved
0x3
(must be zero)
1
The 1's complement of this sum is placed in the checksum field.
6 - 3
Bit
Bit
2
1
0
Bit
Bit
2
1
0
February 1, 2011
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