Datasheet

and all the data bytes as they were sent by the bus mas-
ter. The DS2431 transmits this CRC only if E[2:0] = 111b.
With the Read Scratchpad command, the CRC is gener-
ated by first clearing the CRC generator and then shifting
in the command code, the target addresses TA1 and TA2,
the E/S byte, and the scratchpad data as they were sent
by the DS2431. The DS2431 transmits this CRC only if
the reading continues through the end of the scratchpad.
For more information on generating CRC values, refer to
Application Note 27.
Figure 13. CRC-16 Hardware Description and Polynomial
SYMBOL DESCRIPTION
RST 1-Wire reset pulse generated by master.
PD 1-Wire presence pulse generated by slave.
Select Command and data to satisfy the ROM function protocol.
WS Command “Write Scratchpad.”
RS Command “Read Scratchpad.”
CPS Command “Copy Scratchpad.”
RM Command “Read Memory.”
TA Target address TA1, TA2.
TA-E/S Target address TA1, TA2 with E/S byte.
<8–T[2:0] bytes> Transfer of as many bytes as needed to reach the end of the scratchpad for a given target address.
<Data to EOM> Transfer of as many data bytes as are needed to reach the end of the memory.
CRC-16 Transfer of an inverted CRC-16.
FF Loop Indenite loop where the master reads FF bytes.
AA Loop Indenite loop where the master reads AA bytes.
Programming Data transfer to EEPROM; no activity on the 1-Wire bus permitted during this time.
1ST
STAGE
2ND
STAGE
3RD
STAGE
4TH
STAGE
7TH
STAGE
8TH
STAGE
6TH
STAGE
5TH
STAGE
X
0
X
1
X
2
X
3
X
4
POLYNOMIAL = X
16
+ X
15
+ X
2
+ 1
INPUT DATA
CRC OUTPUT
X
5
X
6
11TH
STAGE
12TH
STAGE
15TH
STAGE
14TH
STAGE
13TH
STAGE
X
11
X
12
9TH
STAGE
10TH
STAGE
X
9
X
10
X
13
X
14
X
7
16TH
STAGE
X
16
X
15
X
8
DS2431 1024-Bit, 1-Wire EEPROM
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Command-Specic 1-Wire Communication Protocol—Legend