NSD–1
Disassembly / Troubleshooting Instructions
PAMS Technical Documentation
Page 7
Issue 2 09/00
Nokia Mobile Phones Ltd.
Watchdog
CCONTs watchdog circuitry consists of an eight bit down counter that
causes CCONT to power down when zero is reached. The counter may
be reset by loading a new, non–zero value into the watchdog register via
CCONTs serial bus. It is difficult to verify the watchdog function, but the
serial bus may be verified.
There is a watchdog disable pin which allows the watchdog timer to ex-
pire without shutting down the phone, but this pin is mainly used as one of
the methods to turn on CCONT from power off mode. While the phone
power key is pressed, this pin should be pulled low and can be checked
at TP29.
The watchdog can be disabled by pulling down the above mentioned
pin(WDDISX) by installing a 0 Ohm resistor at R307, and removing R325.
Serial bus
Since the serial bus is used to control almost all of CCONTs functions,
any shorts or open circuits on these three lines would cause CCONT to
be completely nonfunctional. The main symptoms are the following:
CCONT will turn on when the power key is pressed (verify this by check-
ing Vbb), but will then power off after 32 seconds. All three serial bus sig-
nals (CCONTCSX, UIF_CCONT_SDIO, and UIF_CCONT_SCLK) should
toggle when attempting to write to a CCONT register.
Note: If the LCD does not come on during this time, however, it may indi-
cate that the serial bus is functional, but phone does not have valid flash
code.
PENTA
PENTA supplies power to the RF section. It has 5 independently switch-
able regulators that are controlled via separate enable pins. There is also
a common enable pin that must be active in order to turn on any of the
regulators. Each of the regulators, P1–P5, should have output voltages
between 2.7V and 2.85V (2.8V nominal). These can be checked at the fol-
lowing test points.
a) P1 – TP16
b) P2 – TP15
c) P3 – TP17
d) P4 – TP18
e) P5 – TP19
External regulators
There are three regulators used in addition to CCONT and PENTA. One
is controlled by CCONTs VR7 regulator output and used as a low noise
power source for RF. This regulator is 2.8V nominal and can be checked
at TP8.
The second regulator is used to power the data cable accessory, so out-
put is enabled only when a data cable accessory is detected. This regu-
lator is also 2.8V nominal and can be checked at TP42 (shares SGND).
