MFRC63002R datasheet(10/118 Pages) NXP

10 / 118 page

MFRC630

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Product data sheet

COMPANY PUBLIC

Rev. 3.1 — 6 September 2012

227531

10 of 118

NXP Semiconductors

MFRC630

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 MFRC630 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

MFRC630 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

Timer

Treload







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