DS1921G Maxim, DS1921G Datasheet - Page 37

• Manufacturer Part Number: DS1921G
• Description: The DS1921G Thermochron® iButton® is a rugged, self-sufficient system that measures temperature and records the result in a protected memory section
• Manufacturer: Maxim

Step 1: Set the RTC
Let the actual time be 15:30:00 hours on Monday, the 1st of April in 2002. This results in the following data to be writ-
ten to the RTC registers:
With only a single DS1921G connected to the bus master, the communication of step 1 is as follows:
ADDRESS
MASTER MODE
DATA
Rx
Rx
Rx
Rx
Rx
Rx
Rx
Rx
Tx
Tx
Tx
Tx
Tx
Tx
Tx
Tx
Tx
Tx
Tx
Tx
Tx
Tx
Tx
Tx
______________________________________________________________________________________
200h
00h
DATA (LSB FIRST)
<7 data bytes>
<7 data bytes>
201h
(Presence)
(Presence)
(Presence)
(Presence)
30h
(Reset)
(Reset)
(Reset)
(Reset)
CCh
CCh
AAh
CCh
0Fh
00h
02h
00h
02h
06h
55h
00h
02h
06h
202h
15h
Reset pulse (480μs to 960μs)
Presence pulse
Issue Skip ROM command
Issue Write Scratchpad command
TA1, beginning offset = 00h
TA2, address = 0200h
Write 7 bytes of data to scratchpad
Reset pulse
Presence pulse
Issue Skip ROM command
Issue Read Scratchpad command
Read TA1, beginning offset = 00h
Read TA2, address = 0200h
Read E/S, ending offset = 6h, flags = 0h
Read scratchpad data and verify
Reset pulse
Presence pulse
Issue Skip ROM command
Issue Copy Scratchpad command
TA1
TA2
E/S
Reset pulse
Presence pulse
203h
01h
Thermochron iButton
(AUTHORIZATION CODE)
204h
81h
COMMENTS
205h
04h
206h
02h
37