7477 datasheet(249/354 Pages) RENESAS

Part #	7477

Description	8-BIT SINGLE-CHIP MICROCOMPUTER 740 FAMILY / 7470 SERIES

PDF	354 Pages

Scroll/Zoom	100%

Manufacturer	RENESAS [Renesas Technology Corp]

Direct Link	http://www.renesas.com

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249 / 354 page

7470/7471/7477/7478 GROUP USER’S MANUAL

2-14

APPLICATION

2.3 Timers

7470

7471

7477

7478

Fig. 2.3.3 Example of measurement method of frequency

2 Event counter mode: Frequency measurement

Outline: The frequency of the pulse input to the CNTR 0 pin (“H” active) is measured by the

number of events in a certain period.

Specifications: A count operation is started specifying the count source of timer 1 as CNTR0.

Timer 2 (count source: f(XIN)/64) detects 1 ms and the frequency of the pulse

input to CNTR0 is calculated from the number of events counted within 1 ms.

Note: The number of events of an input pulse is specified as 255 or less within 1 ms.

Figure 2.3.3 shows an example of measurement method of frequency and Figure 2.3.4 shows an

example of control procedure.

,,,,

CNTR0

kHz

Timer 2 interrupt request bit

Count start

Count stop

Count start

Count stop

X times

1 ms

q Pulse frequency of CNTR

1 ms has elapsed

input =

7477 Datasheet(PDF) 249 Page - Renesas Technology Corp