Datasheet

DS1977
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MASTER MODE
DATA (LSB FIRST)
COMMENTS
Password Address)
TX 7Fh TA2, Target Address = 7FC8h
TX <Full-Access Password> Transmit Full-Access Password
(—) (Activate Strong Pullup for t
PROG
) Supply Power for Password Comparison
RX AAh Check for Password Match; AAh = Match
TX (Reset) Reset Pulse
RX (Presence) Presence Pulse
Step 5 TX CCh Issue Skip ROM Command
TX 0Fh Issue Write Scratchpad Command
TX D0h
TA1, Target Address = D0h (Password
Control Register Address)
TX 7Fh TA2, Target Address = 7FD0h
TX AAh Write Password Enabling Pattern
TX (Reset) Reset Pulse
RX (Presence) Presence Pulse
TX CCh Issue Skip ROM Command
TX AAh Issue Read Scratchpad Command
RX D0h Read TA1, Target Address = D0h
RX 7Fh Read TA2, Target Address = 7FD0h
RX 10h Read E/S-Byte
RX AAh Verify Password Enabling Pattern
TX (Reset) Reset Pulse
RX (Presence) Presence Pulse
TX CCh Issue Skip ROM Command
TX 99h
Issue Copy Scratchpad with Password
Command
TX D0h TA1, Target Address = D0h
TX 7Fh TA2, Target Address = 7FD0h
TX 10h E/S-Byte
TX <8 Bytes>
Transmit 8 Dummy Bytes as Password,
Because Passwords are Not Yet Enabled
(—) (Activate Strong Pullup for t
PROG
) Supply Power for Programming
RX AAh
Read to Check for Programming Success;
AAh Means Success
TX (Reset) Reset Pulse
RX (Presence) Presence Pulse
Instead of always using Skip ROM, one could use Read ROM first to learn the device's ROM identification (see
Example 1). For the next access one would use the Match ROM command and send the correct ROM identification
to address the device. Subsequent accesses could use the Resume command. This procedure ensures that
devices cannot be swapped during a communication session.
EXAMPLE 3
Task: write 10 data bytes starting at address 00A0h in page 2; read memory pages 2 and 3. The device has
passwords installed and activated. This task is broken into the following steps:
1. Write data to scratchpad
2. Read Scratchpad
3. Copy scratchpad
4. Read the entire memory page 3
5. Continue reading through the end of page 4