Datasheet

Thermochron iButton Device
Maxim Integrated 35
DS1921G
Command-Specific 1-Wire Communication Protocol—Color Codes
Master-to-Slave Slave-to-Master
<data to EOS> FF loopRST
CPS
RST
WS
RS
TA CRC-16
<data to EOS>
<data to EOM>
FF loop
FF loop
00 loop
CRC-16TA-E/S
TA-E/S
CPS TA-E/S
<data>WS TA
TA
Write Scratchpad, Reaching the End of the Scratchpad
PD
PD
Select
RST
Write Scratchpad, Not Reaching the End of the Scratchpad
PD Select
RST
Read Scratchpad
PD Select
Busy
AA loopRST
RM
Copy Scratchpad (Success)
PD Select
RST
Copy Scratchpad (Invalid TA-E/S)
PD Select
RST
Read Memory (Success)
PD Select
00 loop
TARMRST
Read Memory (Invalid Address)
PD Select
Reading reserved pages 20 through 63 or 68 through 127 or pages 192 and higher (beyond data-log memory)
results in 00h bytes.
Command-Specific 1-Wire Communication Protocol—Legend
(continued)
SYMBOL DESCRIPTION
<data> Transfer of an undetermined amount of data
CRC-16 Transfer of an inverted CRC-16
FF loop Indefinite loop where the master reads FFh bytes
AA loop Indefinite loop where the master reads AAh bytes
Busy
Interval during Copy Scratchpad where the DS1921G does not respond. Any bits read during this time
are logic 1.
00 loop Indefinite loop where the master reads 00h bytes
1-Wire Communication Examples