dsPIC33F/PIC24H Family Reference Manual
DS70205C-page 11-22 © 2010 Microchip Technology Inc.
11.9 PERIPHERALS USING TIMER MODULES
11.9.1 Time Base for Input Capture and Output Compare
The input capture and output compare peripherals can select Timer2 or Timer3 as the time base.
For further details, refer to Section 12. “Input Capture” (DS70198), Section 13. “Output
Compare” (DS70209) and the specific device data sheet.
11.9.2 A/D Special Event Trigger
On each device variant, one Type C timer has the capability to generate a special A/D conversion
trigger signal on a period match, in both 16- and 32-bit modes. The Timer module provides a
conversion start signal to the A/D sampling logic.
•If T32=0, when a match occurs between the 16-bit timer register (TMRx) and the
respective 16-bit period register (PRx), the A/D Special Event Trigger signal is generated
•If T32=1, when a match occurs between the 32-bit timer (TMRx:TMRy) and the 32-bit
respective combined period register (PRx:PRy), the A/D Special Event Trigger signal is
generated
The Special Event Trigger signal is always generated by the timer. The trigger source must
be selected in the A/D Converter control registers. For additional information, refer to
Section 16. “Analog-to-Digital Converter (ADC)” (DS70183) and the specific device data
sheet.
11.9.3 Timer as an External Interrupt Pin
The external clock input pin for each timer can be used as an additional interrupt pin. To provide
the interrupt, the timer period register, PRx, is written with a non-zero value and the TMRx
register is initialized to a value of one less than the value written to the period register. The timer
must be configured for a 1:1 clock prescaler. An interrupt is generated when the next rising edge
of the external clock signal is detected.
11.9.4 I/O Pin Control
When a Timer module is enabled and configured for external clock or gate operation, the user
application must ensure the I/O pin direction is configured for an input. Enabling the Timer
module does not configure the pin direction.
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