DS1977 Maxim, DS1977 Datasheet - Page 23

• Manufacturer Part Number: DS1977
• Description: The DS1977 is a 32KB EEPROM in a rugged iButton® enclosure
• Manufacturer: Maxim

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