DS2703 Datasheet, PDF (19/20 Pages) Dallas Semiconductor – SHA-1 Battery Pack Authentication IC

DS2703 SHA-1 Battery Pack Authentication IC
COMPUTATION AND PROGRAMMING
The Compute Next Secret operation waveform is shown in Figure 11. The user issues a 1-Wire reset followed by a
Skip ROMID command, Match ROMID plus the ROMID, Search or Read Net, followed by the Compute Next Secret
command. The system host must connect the low impedance source to the DQ line within time t_D and for a duration
of time t_SHA. The DQ line is then pulled to V_PP for t_PPW milliseconds and then returned to nominal voltage. The fast
rise and fall time requirements for the programming pulse are required to prevent damage during the transition
between normal communication mode and programming mode.
Figure 11. Compute Next Secret Function Command
t_PPR
t_PPW
t_PPF
t_D
t_SHA
1-Wire SKIP ROM
Reset
Cmd
Presence
Pulse
Compute
Next Secret
Cmd
Apply Low
Impedance
Pull-up
Apply
Programming
Pulse
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