Service manual

June 21,2004 2-3
NP88 FLEX DECODER
Operating Modes
Data-decoding Interval - FLEX Pager
When t he pager powers up, the receiver is turned on, and the decoder begins to
search for a valid FLEX frame. When a valid FLEX frame is detected, the pager
performs the following sequence of operations:
a. synchronizes to the channel
b. searches for the pager’s FLEX address
c. begins to operate at the desired collapse value
d. changes to the page alert/display mode
If no frame is detected within the programmed time (1 to 4 minutes), the pager
enters a baud detect mode to conserve battery power. While in baud detect mode,
thepager searchesevery 1.6secondstodetermine ifthereisanyFLEX information
on the channel.
If no address is detected after channel synchronization, the pager shuts off the
receiver and decoder circuits and enters a lower current consumption mode and
remains in that mode until the next FLEX frame is due on the channel.
Page Alert/Display Mode
Either an incoming message or a button press changes operating modes from pag e
search mode to page alert/display mode.
Button Press
If a button is pressed, an interrupt is generated in the microcomputer (µC) and the
software determines which button was pressed and the correct response. The µC
turns on the voltage mul tiplier that is internal to t he LCD module causing the
respective LCD pixels pattern to be visible.
Incoming Message
If thedisplay modeisentered duetoanincoming message,the page isdecodedand
the
µC generates signals to the Support Module to produce an alert pattern
TheµCwritesthemessagedatatotheLCD driverand turnsonthe display.Certain
messages such as the time and date are stored within the µC itself.
The Support Module drives the Transducer to produce a n audible2731 Hz tone
pattern (tone alert) which lasts for a pre-selected period of time. The tone pattern
is controlled by the µC.
The tonealertca n b e stopped before the programmedtimehaselapsed by pressing
any button. The µC is programmed to sense this and halt the signals to the
Transducer. Pressing the ON/READ/SELECT (W) button after silencing the alert
causes the message to be displayed. The button information is decoded by the
Support Module and the information is transferred to the
µC
for a nalysis.
Pagers operating in the silent mode will not produce a tone alert. Instead, when a
pageisreceived,onlytheVibratorandAlertLampareactivated.Acompletelysilent
pager option is also available.