7733 datasheet(188/940 Pages) RENESAS

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TIMER B

7733 Group User’s Manual

7–25

7.5 Pulse period/Pulse width measurement mode

(Bits 1 and 0 of timer Bi mode register = “102”)

In this mode, an external signal’s pulse period or pulse width is measured. (Refer to Table 7.5.1.) Figure

7.5.1 shows the structures of the timer Bi mode register and timer Bi register in the pulse period/pulse width

measurement mode.

s Pulse period measurement

The pulse period of an external signal which is input to pin TBiIN is measured.

s Pulse width measurement

The pulse width (“L” level width and “H” level width) of an external signal which is input to pin TBiIN is

measured.

Note: When the port-Xc selection bit (bit 4 at address 6C16) = “1,” timer B2 functions as a clock timer.

Accordingly, pulse period/pulse width measurement cannot be performed.

Table 7.5.1 Specifications of pulse period/pulse width measurement mode

Item

Count source

Count operation

Count start condition

Count stop condition

Interrupt request occurrence timing

Pin TBiIN’s function

Read from timer

Write to timer

Specifications

Clock f2, f16, f64, or f512

q Countup

q When valid edge of the measurement pulse is input, the counter

value is transferred to the reload register. And then, the counter

value is cleared to “000016,” and counting is continued.

When the count start flag is set to “1.”

When the count start flag is cleared to “0.”

q When the valid edge of the measurement pulse is input (Note 1).

q At an overflow (Simultaneously, the overflow flag is set to “1.”)

Measurement pulse input

By reading the timer Bi register, the reload register’s contents

(Measurement result) is read out (Note 2).

Ignored

Clocks f2, f16, f64, and f512: Refer to chapter “14. CLOCK GENERATING CIRCUIT.”

Overflow flag: A flag used to identify the source of an interrupt request occurrence.

Notes 1: An interrupt request is not generated when the first valid edge is input after counting starts.

2: From when counting starts until the second valid edge is input, a value obtained by reading the

timer Bi register is undefined.

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