UPD75216ACW

Manufacturer Part NumberUPD75216ACW
Description4-BIT SINGLE-CHIP MICROCOMPUTER
ManufacturerNEC
UPD75216ACW datasheet
 


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Page 20/72:

WATCH TIMER

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5.4

WATCH TIMER

The PD75216A incorporates one channel of watch timer. The watch timer has the following functions.
Sets the test flag (IRQW) at 0.5 sec 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.
f
XX
128
From
f
(32.768 kHz)
Selector
Clock
(32.768 kHz)
Generator
f
XT
(32.768 kHz)
WM
WM7 WM6 WM5 WM4
Remarks
Values at f
XX
20
Fig. 5-3 Watch Timer Block Diagram
f
W
(256 Hz : 3.91 ms)
7
2
W
Frequency Divider
f
W
Clear
(2.048 kHz)
16
P23
Output
WM3
WM2 WM1 WM0
Latch
8
Internal Bus
= 4.194304 MHz and f
= 32.768 kHz are indicated in parentheses.
XT
PD75216A
INTW
IRQW
Selector
f
W
Set Signal
14
2
2Hz
0.5 sec
Output Buffer
P23/BUZ
PORT2.3
Bit 2 of PMGB
Port 2
Input/Output
Mode