M38047FEHKP datasheet(169/387 Pages) RENESAS

169 / 387 page

2-45

APPLICATION

2.3 Timer

Rev.1.00 Jan 14, 2005

REJ09B0212-0100Z

3804 Group (Spec.H)

2.3.4 Notes on timer

Notes on 8-bit timer (timer 1, 2, X, Y)

q If a value n (between 0 and 255) is written to a timer latch, the frequency division ratio is 1/(n+1).

q When switching the count source by the timer 12, X and Y count source selection bits, the value

of timer count is altered in unconsiderable amount owing to generating of thin pulses in the count

input signals.

Therefore, select the timer count source before set the value to the prescaler and the timer.

q Set the double-function port of the CNTR0/CNTR1 pin and port P54/P55 to output in the pulse output

mode.

q Set the double-function port of CNTR0/CNTR1 pin and port P54/P55 to input in the event counter

mode and the pulse width measurement mode.

Notes on 16-bit timer (timer Z)

(1)

Pulse output mode

q Set the double-function port of the CNTR2 pin and port P47 to output.

(2)

Pulse period measurement mode

q Set the double-function port of the CNTR2 pin and port P47 to input.

q A read-out of timer value is impossible in this mode. The timer can be written to only during timer

stop (no measurement of pulse period).

q Since the timer latch in this mode is specialized for the read-out of measured values, do not

perform any write operation during measurement.

q “FFFF16” is set to the timer when the timer underflows or when the valid edge of measurement

start/completion is detected. Consequently, the timer value at start of pulse period measurement

depends on the timer value just before measurement start.

(3)

Pulse width measurement mode

q Set the double-function port of the CNTR2 pin and port P47 to input.

q A read-out of timer value is impossible in this mode. The timer can be written to only during timer

stop (no measurement of pulse period).

q Since the timer latch in this mode is specialized for the read-out of measured values, do not

perform any write operation during measurement.

q “FFFF16” is set to the timer when the timer underflows or when the valid edge of measurement

start/completion is detected. Consequently, the timer value at start of pulse width measurement

depends on the timer value just before measurement start.

(4)

Programmable waveform generating mode

q Set the double-function port of the CNTR2 pin and port P47 to output.

(5)

Programmable one-shot generating mode

q Set the double-function port of CNTR2 pin and port P47 to output, and of INT1 pin and port P42 to

input in this mode.

q This mode cannot be used in low-speed mode.

q If the value of the CNTR2 active edge switch bit is changed during one-shot generating enabled

or generating one-shot pulse, then the output level from CNTR2 pin changes.

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