MC68HC705P9CS datasheet(103/160 Pages) FREESCALE

103 / 160 page

Timer

Operation

MC68HC705P9 — Rev. 4.0

Technical Data

MOTOROLA

Timer

103

9.4.1 Pin Functions

The timer uses two pins.

9.4.1.1 PD7/TCAP

PD7/TCAP is the input capture pin. When an active edge occurs on

PD7/TCAP, the timer transfers the current counter value to the input

capture registers. PD7/TCAP is also an I/O port pin.

9.4.1.2 TCMP

TCMP is the output-only output compare pin. When the counter value

matches the value written in the output compare registers, the timer

transfers the output level bit, OLVL, to the TCMP pin.

9.4.2 Input Capture

The input capture function is a means to record the time at which an

external event occurs. When the input capture circuitry detects an active

edge on the PD7/TCAP pin, it latches the contents of the timer registers

into the input capture registers. The polarity of the active edge is

programmable.

Latching values into the input capture registers at successive edges of

the same polarity measures the period of the input signal on the

PD7/TCAP pin. Latching the counter values at successive edges of

opposite polarity measures the pulse width of the signal. Figure 9-3

shows the logic of the input capture function.

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