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CLRC663 Datasheet(PDF) 10 Page - NXP Semiconductors |
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CLRC663 Datasheet(HTML) 10 Page - NXP Semiconductors |
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10 / 132 page 
CLRC663 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2012. All rights reserved. Product data sheet COMPANY PUBLIC Rev. 3.3 — 3 April 2012 171133 10 of 132 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: (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. Timer value value T Timer Treload T * |
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