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54 page 
EventCounterMode In this mode, a number of externally changing logic events, occurring on the external timer TCn pin, can be recorded by the Timer/Event Counter. To operate in this mode, the Operating Mode Select bit pair, TnM1/TnM0, in the Timer Control Register must be set to the correct value as shown. ControlRegisterOperatingMode SelectBitsfortheEventCounterMode Bit7 Bit6 0 1 In this mode, the external timer TCn pin, is used as the Timer/Event Counter clock source, however it is not divided by the internal prescaler. After the other bits in the Timer Control Register have been setup, the enable bit TnON, which is bit 4 of the Timer Control Register, can be set high to enable the Timer/Event Counter to run. If the Active Edge Select bit, TnEG, which is bit 3 of the Timer Control Register, is low, the Timer/Event Counter will increment each time the external timer pin receives a low to high transition. If the TnEG is high, the counter will increment each time the external timer pin receives a high to low transition. When it is full and overflows, an interrupt signal is generated and the Timer/Event Counter will reload the value already loaded into the preload register and continue counting. The interrupt can be disabled by ensuring that the Timer/Event Counter Interrupt Enable bit in the corresponding Interrupt Control Register, is reset to zero. As the external timer pin is shared with an I/O pin, to ensure that the pin is configured to operate as an event counter input pin, two things have to happen. The first is to ensure that the Operating Mode Select bits in the Timer Control Register place the Timer/Event Counter in the Event Counting Mode, the second is to ensure that the port control register configures the pin as an input. It should be noted that in the event counting mode, even if the microcontroller is in the Sleep Mode, the Timer/Event Counter will continue to record externally changing logic events on the timer input TCn pin. As a result when the timer overflows it will generate a timer interrupt and corresponding wake-up source. PulseWidthCaptureMode In this mode, the Timer/Event Counter can be utilised to measure the width of external pulses applied to the external timer pin. To operate in this mode, the Operating Mode Select bit pair, TnM1/TnM0, in the Timer Control Register must be set to the correct value as shown. ControlRegisterOperatingMode SelectBitsforthePulseWidthCaptureMode Bit7 Bit6 1 1 In this mode the internal clock, fSYS , fSYS/4 or the LXT, is used as the internal clock for the 8-bit Timer/Event Counter. However, the clock source, fSYS, for the 8-bit timer is further divided by a prescaler, the value of which is determined by the Prescaler Rate Select bits TnPSC2~TnPSC0, which are bits 2~0 in the Timer Control Register. After the other bits in the Timer Control Register have been setup, the enable bit TnON, which is bit 4 of the Timer Control Register, can be set high to enable the Timer/Event Counter, however it will not actually start counting until an active edge is received on the external timer pin. If the Active Edge Select bit TnEG, which is bit 3 of the Timer Control Register, is low, once a high to low transition has been received on the external timer pin, the Timer/Event Counter will start counting until the external timer pin returns to its original high level. At this point the enable bit will be automatically reset to zero and the Timer/Event Counter will stop counting. If the Active Edge Select bit is high, the Timer/Event Counter will begin counting once a low to high transition has been received on the external timer pin and stop counting when the external timer pin returns to its original HT46R064D/065D/066D EnhancedA/DType8-Bit OTP MCU withLEDDriver Rev.1.00 49 January12,2011 T i m e r + 2 E x t e r n a l E v e n t I n c r e m e n t T i m e r C o u n t e r T i m e r + 3 T i m e r + 1 EventCounterModeTimingChart(TnEG=1) |
