DS1921 DALLAS [Dallas Semiconductor], DS1921 Datasheet - Page 36

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

MISSION EXAMPLE: PREPARE AND START A NEW MISSION
Assumption: The previous mission has come to an end. To end an ongoing mission write the MIP bit in
the Status Register to 0.
The preparation of a DS1921H/Z for a mission including the start of the mission requires up to four steps:
STEP 1
Let the actual time be 15:30:00 hours on Monday, the 1
data to be written to the RTC registers:
With only a single DS1921H/Z connected to the bus master, the communication of step 1 is as follows:
Address:
Step 1: set the RTC (if it needs to be adjusted)
Step 2: clear the data of the previous mission
Step 3: set the search condition and mission start delay, clear alarm flags
Step 4: set the temperature alarms and write the sample rate to start the mission
Data:
MASTER MODE
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
201h
30h
DATA (LSB FIRST)
<7 data bytes>
<7 data bytes>
(Presence)
(Presence)
(Presence)
(Presence)
(Reset)
(Reset)
(Reset)
(Reset)
CCh
CCh
CCh
AAh
0Fh
00h
02h
00h
02h
06h
55h
00h
02h
06h
202h
15h
36 of 44
st
203h
01h
of April in 2002. This results in the following
COMMENTS
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
204h
81h
(AUTHORIZATION CODE)
205h
04h
DS1921H/Z
206h
02h