3886 datasheet(148/380 Pages) RENESAS

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3886 Group User’s Manual

APPLICATION

2-31

2.3 Timer

PREX

255

Timer XY mode register (address 23 16)

Timer X operating mode: Timer mode

Timer X count: Stop

Clear to “0” when starting count.

Prescaler X (address 24 16)

Timer X (address 25 16)

Set “division ratio – 1”

ICON1

Timer X interrupt: Enabled

Interrupt control register 1 (address 3E 16)

IREQ1

Interrupt request register 1 (address 3C 16)

Timer X interrupt request

(becomes “1” at 250 ms intervals)

Fig. 2.3.12 Relevant registers setting

(2)

Timer application example 1: Clock function (measurement of 250 ms)

Outline: The input clock is divided by the timer so that the clock can count up at 250 ms intervals.

Specifications: •The clock f(XIN) = 4.19 MHz (222 Hz) is divided by the timer.

•The clock is counted up in the process routine of the timer X interrupt which occurs

at 250 ms intervals.

Figure 2.3.11 shows the timers connection and setting of division ratios; Figure 2.3.12 shows the

relevant registers setting; Figure 2.3.13 shows the control procedure.

Fig. 2.3.11 Timers connection and setting of division ratios

f(XIN) = 4.19 MHz

250 ms

1/16

1/256

1/4

1 second

Dividing by 4 with software

Fixed

Prescaler X

Timer X

Timer X interrupt

request bit

0 or 1

0 : No interrupt request issued

1 : Interrupt request issued

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