DS1921 DALLAS [Dallas Semiconductor], DS1921 Datasheet - Page 38

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

STEP 3
In this example, the rollover is disabled and the search condition is set for a high temperature only. The
mission is to start with a delay of 90 (005Ah) minutes and the alarm flags TLF, THF, and TAF are
cleared. This results in the following data to be written to the special function registers:
* Writing through address locations 20Fh to 211h is faster than accessing the Mission Start Delay
With only a single DS1921H/Z connected to the bus master, the communication of step 3 is as follows:
Address:
Register in a separate cycle. The write attempt has no effect on the contents of these registers.
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
20Eh
02h
20Fh
00h*
DATA (LSB FIRST)
<7 data bytes>
<7 data bytes>
(Presence)
(Presence)
(Presence)
(Presence)
(Reset)
(Reset)
(Reset)
(Reset)
CCh
CCh
CCh
AAh
0Fh
0Eh
0Eh
0Eh
02h
02h
14h
55h
02h
13h
210h
00h*
38 of 44
211h
00h*
COMMENTS
Reset pulse (480µs to 960µs)
Presence pulse
Issue Skip ROM command
Issue Write Scratchpad command
TA1, beginning offset = 0Eh
TA2, address = 020Eh
Write 7 bytes of data to scratchpad
Reset pulse
Presence pulse
Issue Skip ROM command
Issue Read Scratchpad command
Read TA1, beginning offset = 0Eh
Read TA2, address = 020Eh
Read E/S, ending offset = 14h, 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
212h
5Ah
(AUTHORIZATION CODE)
213h
00h
DS1921H/Z
214h
00h