DS1921 DALLAS [Dallas Semiconductor], DS1921 Datasheet - Page 33

• Manufacturer Part Number: DS1921
• Description: High-Resolution Thermochron iButton
• Manufacturer: DALLAS [Dallas Semiconductor]

CRC-16 HARDWARE DESCRIPTION AND POLYNOMIAL Figure 16
Command-Specific 1-Wire Communication Protocol — Legend
X
X
0
8
STAGE
STAGE
<data to EOM>
<data to EOS>
<data to EOP>
<00 to EOP>
1
9
<32 bytes>
th
st
Symbol
CRC16\
AA loop
FF loop
00 loop
TA-E/S
<data>
Select
RMC
RST
CPS
WS
RM
CM
PD
RS
CT
TA
X
X
9
1
STAGE
STAGE
10
2
nd
th
X
10
STAGE
Transfer of an inverted CRC16
Description
1-Wire Reset Pulse generated by master
1-Wire Presence Pulse generated by slave
Command and data to satisfy the ROM function protocol (Skip ROM, Search ROM, etc.)
Command "Write Scratchpad"
Command "Read Scratchpad"
Command "Copy Scratchpad"
Command "Read Memory"
Command "Read Memory with CRC"
Command "Clear Memory"
Command "Convert Temperature"
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 1Fh
Transfer of as many data bytes as are needed to reach the end of a memory page
Transfer of as many data bytes as are needed to reach the end of the datalog memory
Transfer of as many 00h bytes as are needed to reach a memory page boundary
Transfer of 32 bytes
Transfer of an undetermined amount of data
Indefinite loop where the master reads FFh bytes
Indefinite loop where the master reads AAh bytes
Indefinite loop where the master reads 00h bytes
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
33 of 44
STAGE
X
16
14
4
STAGE
th
+ X
5
th
X
15
14
+ 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
DS1921H/Z