DS2703 Dallas Semiconductor, DS2703 Datasheet - Page 17

• Manufacturer Part Number: DS2703
• Description: SHA-1 Battery Pack Authentication IC
• Manufacturer: Dallas Semiconductor

DS2703 SHA-1 Battery Pack Authentication IC
LOW-IMPEDANCE DQ DURING COMPUTATION
The SHA-1 computation requires more current than the DQ pullup resistor used during normal communication can
supply. During the computation, the DQ source impedance must be reduced to maintain power to the device under
the higher load condition. The user must connect the low impedance source to the DQ line within t
of issuing any
D
command to perform a computation, and return the DQ source to normal settings before reading or writing to the
one-wire interface. See Figure 9.
Figure 9. Compute MAC Function Command
t
t
D
SHA
Apply Low
1-Wire
SKIP ROM
Compute
Up to 160 Read Time Slots
Impedance
Reset
Cmd
MAC
(Read 20-Byte MAC)
8 Write 0
Pull-up
Cmd
Time Slots
Presence
Pulse
17 of 20