CLRC663 Datasheet, PDF (10/132 Pages) NXP Semiconductors – Contactless reader IC

NXP Semiconductors
CLRC663
Contactless reader IC
8.2.1 Timer modes
8.2.1.1 Time-Out- and Watch-Dog-Counter
Having configured the timer by setting register T(x)ReloadValue and starting the counting
of Timer(x) by setting bit TControl.T(x)StartStop and TControl.T(x)Running, the timer unit
decrements the T(x)CounterValue Register beginning with the configured start event. If
the configured stop event occurs before the Timer(x) underflows (e.g. a bit is received
from the card), the timer unit stops (no interrupt is generated).
If no stop event occurs, the timer unit continues to decrement the counter registers until
the content is zero and generates a timer interrupt request at the next clock cycle. This
allows to indicate to a host that the event did not occur during the configured time interval.
8.2.1.2 Wake-up timer
The wake-up Timer4 allows to wakeup the system from standby after a predefined time.
The system can be configured in such a way that it is entering the standby mode again in
case no card had been detected.
This functionality can be used to implement a low-power card detection (LPCD). For the
low-power card detection it is recommended to set T4Control.T4AutoWakeUp and
T4Control.T4AutoRestart, to activate the Timer4 and automatically set the system in
standby. The internal low-power clock oscillator (LPO) is then used as input clock for this
Timer4. If a card is detected the host-communication can be started. If bit
T4Control.T4AutoWakeUp is not set, the CLRC663 will not enter the standby mode again
in case no card is detected but stays fully powered.
8.2.1.3 Stop watch
The elapsed time between a configured start- and stop event may be measured by the
CLRC663 timer unit. By setting the registers T(x)ReloadValueHi, T(x)reloadValueLo the
timer starts to decrement as soon as activated. If the configured stop event occurs, the
timers stops decrementing. The elapsed time between start and stop event can then be
calculated by the host dependent on the timer interval TTimer:
   T  Treload _value  Timer _value * T _Timer
(1)
If an underflow occurred which can be identified by evaluating the corresponding IRQ bit,
the performed time measurement according to the formula above is not correct.
8.2.1.4 Programmable one-shot timer
The host configures the interrupt and the timer, starts the timer and waits for the interrupt
event on pin IRQ. After the configured time the interrupt request will be raised.
8.2.1.5 Periodical trigger
If the bit T(x)Control.T(x)AutoRestart is set and the interrupt is activated, an interrupt
request will be indicated periodically after every elapsed timer period_.
CLRC663
Product data sheet
COMPANY PUBLIC
All information provided in this document is subject to legal disclaimers.
Rev. 3.3 — 3 April 2012
171133
© NXP B.V. 2012. All rights reserved.
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