Datasheet

DS1977
23 of 29
Figure 13. CRC16 HARDWARE DESCRIPTION AND POLYNOMIAL
Polynomial = X
16
+ X
15
+ X
2
+ 1
X
0
X
1
X
2
X
3
X
4
X
5
X
6
X
7
X
8
X
9
X
10
X
11
X
12
X
13
X
14
X
15
X
16
1
st
STAGE
2
nd
STAGE
3
rd
STAGE
4
th
STAGE
6
th
STAGE
5
th
STAGE
7
th
STAGE
8
th
STAGE
9
th
STAGE
10
th
STAGE
11
th
STAGE
12
th
STAGE
13
th
STAGE
14
th
STAGE
15
th
STAGE
16
th
STAGE
INPUT DATA
CRC
OUTPUT
COMMAND-SPECIFIC 1-Wire COMMUNICATION PROTOCOL—LEGEND
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 with Password"
RM Command "Read Memory with Password"
VP Command "Verify Password"
RV Command "Read Version"
TA Target Address TA1, TA2
TA-E/S Target Address TA1, TA2 with E/S Byte
<data to EOS> Transfer of as Many Data Bytes as are Needed to Reach the Scratchpad Offset 3Fh
<data to EOP> Transfer of as Many Data Bytes as are Needed to Reach the End of a Memory Page
<PW/dummy> Transfer of 8 Bytes that Either Represent a Valid Password or Acceptable Dummy Data
<64 bytes> Transfer of 64 Bytes
<data> Transfer of an Undetermined Amount of Data
00h Transmission of One Byte 00h
Password Transmission of Password
Version Transmission of Device Version Number
CRC16\ Transfer of an Inverted CRC16
FF loop Indefinite Loop Where the Master Reads FF Bytes
AA loop Indefinite Loop Where the Master Reads AA Bytes
Strong Pullup
Data Transfer to/from EEPROM (Data or Passwords Memory); No Activity on the 1-Wire
Bus Permitted During this Time