SLRC400 Datasheet, PDF (77/130 Pages) NXP Semiconductors – I·CODE Reader IC

Philips Semiconductors
I•CODE Reader IC
Product Specification Rev. 2.0 November 2001
SL RC400
9.3 Usage of the Timer Unit
9.3.1 TIME-OUT- AND WATCH-DOG-COUNTER
Having started the timer by setting TReloadValue the timer unit decrements the TimerValue Register
beginning with a certain start event. If a certain stop event occurs e.g. a bit is received from the label, the
timer unit stops (no interrupt is generated).
On the other hand, if no stop event occurs, e.g. the label does not answer in the expected time, the timer unit
decrements down to zero and generates a timer interrupt request. This signals indicate the µ-Processor that
the expected event has not occurred in the given time T_Timer.
9.3.2 STOP WATCH
The time T_Timer between a certain start- and stop event may be measured by the µ-Processor by means of
the SL RC400 timer unit. Setting TReloadValue the timer starts to decrement. If the defined stop event
occurs the timers stops. The time between start and stop can be calculated by
( ) ∆T = T Re load _value−Timer_value *T_Timer
if the timer does not decrements down to zero.
9.3.3 PROGRAMMABLE ONE-SHOT TIMER
The µ-Processor starts the timer unit and waits for the timer interrupt. After the specified time T_Timer the
interrupt will occur (TautoRestart = 0).
9.3.4 PERIODICAL TRIGGER
If the µ-Processor sets bit TautoRestart and TreloadValue not equal 0, it will generate an interrupt request
periodically after every T_Timer.
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Preliminary