Datasheet

DS1921G
Step 2: Clear the data of the previous mission
Set the EMCLR bit to 1, enable the RTC, and then execute the Clear Memory command. The RTC oscillator must be
stable before the Clear Memory command is issued. Wait 500µs after issuing the Clear Memory command before
proceeding to step 3. This results in the following data to be written to the Status register:
With only a single DS1921G connected to the bus master, the communication of step 2 is as follows:
Thermochron iButton
38 ______________________________________________________________________________________
ADDRESS 20Eh
DATA 40h
MASTER MODE DATA (LSB FIRST) COMMENTS
Tx (Reset) Reset pulse (480µs to 960µs)
Rx (Presence) Presence pulse
Tx CCh Issue Skip ROM command
Tx 0Fh Issue Write Scratchpad command
Tx 0Eh TA1, beginning offset = 0Eh
Tx 02h TA2, address = 020Eh
Tx 40h Write status byte to scratchpad
Tx (Reset) Reset pulse
Rx (Presence) Presence pulse
Tx CCh Issue Skip ROM command
Tx AAh Issue Read Scratchpad command
Rx 0Eh Read TA1, beginning offset = 0Eh
Rx 02h Read TA2, address = 020Eh
Rx 0Eh Read E/S, ending offset = 0Eh, flags = 0h
Rx 40h Read scratchpad data and verify
Tx (Reset) Reset pulse
Rx (Presence) Presence pulse
Tx CCh Issue Skip ROM command
Tx 55h Issue Copy Scratchpad command
Tx 0Eh TA1
Tx 02h TA2
Tx 0Eh E/S
(AUTHORIZATION CODE)
Tx (Reset) Reset pulse
Rx (Presence) Presence pulse
Tx CCh Issue Skip ROM command
Tx 3Ch Issue Clear Memory command
Tx (Reset) Reset pulse
Rx (Presence) Presence pulse