7906 datasheet(170/531 Pages) RENESAS

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7906 Group User’s Manual Rev.2.0

8-19

TIMER B

8.5 Pulse period/Pulse width measurement mode

In this mode, the timer measures an external signal’s pulse period or pulse width. Tables 8.5.1 and 8.5.2

list the specifications of the pulse period/pulse width measurement mode. Figure 8.5.1 shows the structures

of the timer Bi register and timer Bi mode register in the pulse period/pulse width measurement mode.

(1)

Pulse period measurement

The timer measures the pulse period of the external signal that is input to the TBiIN pin.

(2)

Pulse width measurement

The timer measures the pulse width (“L” level and “H” level widths) of the external signal that is input

to the TBiIN pin.

Table 8.5.1 Specifications of pulse period/pulse width measurement mode (when counter clear type is selected)

Item

Count source fi

Count operation

Count start condition

Count stop condition

Interrupt request occurrence timing

TBiIN pin’s function

Read from timer Bi register

Write to timer Bi register

Timer Bi overflow flag: This bit is used to identify the source of an interrupt request occurrence.

Notes 1: No interrupt request occurs when the first valid edge is input after the counter starts counting.

2: When using timer B2, make sure that the timer B2 clock source select bit (see Figure 8.4.2.) to

“0.”

3: The value read out from the timer Bi register is undefined in the period after the counter starts

counting until the second valid edge is input.

Specifications

f2, f16, f64, or f512

q Countup

q Counter value is transferred to the reload register at valid edge of

measurement pulse, and counting continues after clearing the counter

value to “000016.”

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

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

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

q When a counter overflow occurs (The timer Bi overflow flag is set

to “1” simultaneously.)

Measurement pulse input pin (Note 2)

The value obtained by reading the timer Bi register is the reload

Invalid

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