Rainbow Electronics DS2705 - Manual (Page 10)

DS2705: SHA-1 Authentication Master
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MASTER PORT (MDQ) FUNCTION COMMANDS
MASTER MODE WRITE CHALLENGE COMMAND
Write Challenge [0Ch, XXXXXXXXXXXXXXXX]. The master mode Write Challenge command sends the 8-byte
(64-bit) challenge to the remote token in preparation for a Compute MAC command.
Figure 3. Write Challenge (MDQ)
SKIP ROM
Cmd
Write
Challenge
CMD
1-Wire
Reset
Presence
Pulse
64 Write Time Slots
(Random Number)
MASTER MODE COMPUTE MAC W/O ROM ID COMMAND
Compute MAC without ROM ID [36h, XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX].
The Compute MAC command executes a MAC computation in the remote token and reads back the 20-byte result.
Figure 4. Compute and Return MAC (MDQ)
8 Write 0
Time Slots
160 Read Time Slots
(20-Byte MAC)
SKIP ROM
Cmd
Compute
MAC
Cmd
1-Wire
Reset
Presence
Pulse
t
SPUD
t
SPUP
Strong
Pull-up Applied