Watchdog System - Nokia 9000i Service Manual

Rae, rak-1 series
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RAE/RAK–1N
Baseband
All devices are powered up at the same time by the PSL+. It supplies the
reset to the ASIC at power up. The ASIC starts the clocks to the DSP and
the MCU. After about 100 ms the PSL+ releases the reset to ASIC.
ASIC releases the resets to MCU and RFI after 256 13 MHz clock cycles.
DSP reset release time from DSP clock activation can be selected from 0
to 255 13MHz clock cycles. In our case it is 255. SIM reset release time is
according to GSM SIM specifications.
To turn off power for the phone, the user presses the PWR key. The MCU
detects this. The MCU cuts off any ongoing call, exits all tasks, acts
inoperative to the user and leaves the PSL+ watchdog without resets.
After power–down delay, the PSL+ cuts off the supply from all circuitry.
In the acting dead state the phone looks to the user like it is off (lights are
off and the display is blank) but internally the baseband is powered and
communication via RBUS is possible. The RF is not powered in acting
dead state.
If charger is connected in the off state, the phone enters the acting dead
state, but the charging indicator in the UI module shows to the user that
the phone is being charged.

Watchdog system

PSL
XPWROFF
Normal operation:
1. MCU tests DSP
2. MCU updates ASIC watchdog timer (> 2Hz)
3. MCU pulses the XPWROFF input on the PSL+ (about 2Hz)
Page 2–20
reset
DSP
1
5
2
POWER
3
Figure 5. Watchdog system
After Sales
Technical Documentation
ASIC
reset
MCU
Original, 08/96
4

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