Service manual

2-2 June21,2004

DECODER NP88 FLEX

Operating Modes

There are three basic modes of operation of the NP88 FLEX decoder:

power-up, page search and page alert/display.

Power-up Mode

NP88FLEXdecoderoperates inoneof twopower-upmodes,depending

on the condition (at or below minimum voltage or good) of the primary battery. If

the primary battery is not present, the pager does not power up.

Primary Battery At or Below Minimum Voltage

If a primary battery is inserted in a pager with the VCC level at or below the

minimum operating voltage 2.8 Vdc , the linear support module issue s

a reset to the µC and the display module, which in effect resets the entire decoder.

The linear support module boosts the primary battery voltage to generate the

3.1 VdcVCCsupplyforthedecoder,andtheµCexecutesitsinitializationcode.With

theperipheralcircuits initialized,apower-up alertis issuedandthepagerproceeds

to enter the page search mode. The primary battery voltage must exceed 1.15 Vdc

for t he pager to power-up in this mode.

Good Primary Battery

A normal power-up occurs when a battery with a minimum output of 1.3 volts is in

the pager at the time the pager is turned on. When the Read button is pressed, the

pager proceeds with a power-up alert and enters the page search mode.

Page Search Mode

Page search is the main operating modeof NP88 FLEX. Pagesearch

modeoperationisdividedintobattery-saveranddata-decodingintervals.Thepager

software determines when the pager shifts from battery-saver mode to data-

decoding mode and back again through the use of one of the µC internal timers.

Page search operation FLEX pagers as follows:

Battery-saver Interval

FLEX pagers utilize battery-saver intervals. During battery-saver

intervals, the µC generally is in a low-speed, low-power mode and the decoder is

operating at a clock frequency of 38.4 kHz for approximately 80% of the time (low-

speed clock rate).

When the pager is not in a battery-saver interval, the µC internal frequency

synthesizerbooststheexternalcrystal frequencyof38.4kHztoa defaultfrequency

of 4.19MHz.