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CLRC663 Datasheet(PDF) 9 Page - NXP Semiconductors |
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CLRC663 Datasheet(HTML) 9 Page - NXP Semiconductors |
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9 / 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 9 of 132 NXP Semiconductors CLRC663 Contactless reader IC 8.2 Timer module Timer module overview The CLRC663 implements five timers. Each of four timers Timer0 to Timer3 has an input clock that can be configured by register T(x)Control to be 13.56 MHz, 212 kHz, (derived from the 27.12 MHz quartz) or to be the underflow event of a Timer. Each timer implements a counter register which is 16 bit wide. A reload value for the counter is defined in a range of 0000h to FFFFh in the registers TxReloadHi and TxReloadLo. The fourth timer Timer4 is intended to be used as a wakeup timer and is connected to the internal LPO (Low-Power Oscillator) as input clock source. The TControl register allows the global start and stop of each of the four timers Timer0 to Timer3. Additionally, this register indicates if one of the timers is running or stopped. Each of the five timers implements an individual configuration register set defining timer reload value (e.g. T0ReloadHi,T0ReloadLo), the timer value (e.g. T0CounterValHi, T0CounterValLo) and the conditions which define start, stop and clockfrequency (e.g. T0Control). The external host may use these timers to manage timing relevant tasks. The timer unit may be used in one of the following configurations: • Time-out counter • Watch-dog counter • Stop watch • Programmable one-shot timer • Periodical trigger The timer unit can be used to measure the time interval between two events or to indicate that a specific event has occurred after an elapsed time. The timer register content is modified by the timer unit, which can be used to generate an interrupt to allow an host to react on this event. The counter value of the timer is available in the registers T(x)CounterValHi, T(x)CounterValLo. The content of these registers is decremented at each timer clock. If the counter value has reached a value of 0000h and the interrupts are enabled for this specific timer, an interrupt will be generated as soon as the next clock is received. If enabled, the timer event can be indicated on the pin IRQ (interrupt request). The bit Timer(x)Irq can be set and reset by the host controller. Depending on the configuration, the timer will stop counting at 0000h or restart with the value loaded from registers T(x)ReloadHi, T(x)ReloadLo. The counting of the timer is indicated by bit TControl.T(x)Running. The timer can be started by setting bits TControl.T(x)Running and TControl.T(x)StartStopNow or stopped by setting the bits TControl.T(x)StartStopNow and clearing TControl.T(x)Running. Another possibility to start the timer is to set the bit T(x)Mode.T(x)Start, this can be useful if dedicated protocol requirements need to be fulfilled. |
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