UPD75212ACW データシートの表示（PDF） - NEC => Renesas Technology

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UPD75212ACW

4-BIT SINGLE-CHIP MICROCOMPUTER

NEC => Renesas Technology 

µPD75212A

5.4 WATCH TIMER

The µPD75212A incorporates one channel of watch timer. The watch timer has the following functions.

• Sets the test flag (IRQW) at 0.5-second intervals.

The standby mode can be released by IRQW.

• 0.5-second interval can be set with the main system clock and subsystem clock.

• The fast mode enables to set 128-time (3.91 ms) interval useful to program debugging and inspection.

• The fixed frequencies (2.048 kHz) can be output to the P23/BUZ pin for use to generate buzzer sound and trim

the system clock oscillator frequency.

• Since the frequency divider can be cleared, the watch can be started from zero second.

Fig. 5-3 Watch Timer Block Diagram

From

Clock

Generator

fXX

128

(32.768 kHz)

fXT

(32.768 kHz)

fW

27

(256 Hz : 3.91 ms)

Selector fW

(32.768 kHz)

Frequency Divider

fW (2.048 kHz) Clear

16

fW

Selector

214

2Hz

0.5 sec

INTW

IRQW

Set Signal

Output Buffer

P23/BUZ

WM

WM7 WM6 WM5 WM4 WM3WM2 WM1 WM0

8

PORT2.3

P23

Output

Latch

Bit 2 of PMGB

Port 2

Input/Output

Mode

Internal Bus

Remarks Values at fXX = 4.194304 MHz and fXT = 32.768 kHz are indicated in parentheses.

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