M16CSLASH62 datasheet(327/621 Pages) RENESAS

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Timer B

Mitsubishi microcomputers

M16C / 62 Group

SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER

312

2.3 Timer B

2.3.1 Overview

The following is an overview for timer B, a 16-bit timer.

(1) Mode

Timer B operates in one of three modes:

(a) Timer mode

The internal count source is counted.

• Operation in timer mode ........................................................................................................... P316

(b) Event counter mode

The number of pulses coming from outside and the number of the timer overflows are counted.

• Operation in event counter mode ............................................................................................. P318

External pulse period or external pulse widths are measured. If pulse period measurement mode is

selected, the periods of input pulses are continuously measured. If pulse width measurement mode

is selected, widths of “H” level pulses and those of “L” level pulses are continuously measured.

• Operation in pulse period measurement mode ........................................................................ P320

• Operation in pulse width measurement mode .......................................................................... P322

(2) Count source

An internal count source can be selected from f1, f8, f32, and fC32. f1, f8, and f32 are clocks obtained by

dividing the CPU main clock by 1, 8, and 32 respectively. fC32 is the clock obtained by dividing the

CPU secondary clock by 32.

(3) Frequency division ratio

The frequency division ratio equals [the value set in the timer register + 1]. The counter underflows

when a count source equal to a frequency division ratio is input, and an interrupt request occurs.

(4) Reading the timer

In timer mode or event counter mode, the count value at the time of reading the timer register will be

read. Read the register in 16-bit increments. In both the pulse period measurement mode and pulse

width measurement mode, an indeterminate value is read until the second effective edge is input after

a count is started, otherwise, the measurement results are read.

(5) Writing to the timer

When writing to the timer register while a count is in progress, the value is written only to the reload

reload register and the count. Write the value in 16-bit increments. The timer register cannot be

written to in either the pulse period measurement mode or the pulse width measurement mode.

M16C/62 Datasheet(PDF) 327 Page - Renesas Technology Corp