UPD75064A データシートの表示（PDF） - NEC => Renesas Technology

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UPD75064A

4-BIT SINGLE-CHIP MICROCOMPUTER

NEC => Renesas Technology 

µPD75064, 75066, 75068, 75064(A), 75066(A), 75068(A)

5.5 Watch Timer

The µPD75068 has an on-chip 1-ch watch timer. The watch timer has the following functions:

• Sets the test flag (IRQW) with a 0.5-sec interval. The standby mode can be released by IRQW.

• The 0.5-second interval can be generated from either the main system clock or subsystem clock.

• The time interval can be made 128 times faster (3.91 ms) by selecting the fast mode. This is convenient

for program debugging, testing, etc.

• Any of the frequencies 2.048 kHz, 4.096 kHz, and 32.768 kHz can be output to the P23/BUZ pin. This

can be used for beep and system clock frequency trimming.

• The frequency divider circuit can be cleared so that a zero-second start of the watch can be made.

Figure 5-4. Watch Timer Block Diagram

fw (256 Hz: 3.91 ms)

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 fX

From the 

clock

generator





128

(32.768 kHz)

fXT

 (32.768 kHz)

fW

(32.768 kHz)

Selector

Frequency divider

(4 kHz)(2 kHz)

fw fw

23 24

Clear signal

fw

Selector

214

2 Hz

0.5 sec

INTW

IRQW

set signal

Selector

Output buffer

P23/BUZ

WM

WM7 0 WM5 WM4 WM3 WM2 WM1 WM0

Bit test instruction

8

Internal bus

PORT2.3

P23 output

latch

Bit 2 of PMGB

Port 2 input/

output mode

Remark ( ) is for fX = 4.194304 MHz, fXT = 32.768 kHz.

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