upd75212a Renesas Electronics Corporation., upd75212a Datasheet - Page 20

• Manufacturer Part Number: upd75212a
• Description: 4-bit Single-chip Microcomputer
• Manufacturer: Renesas Electronics Corporation.

20
Remarks
5.4
From
Clock
Generator
The PD75212A 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.
WATCH TIMER
Values at f
f
128
(32.768 kHz)
(32.768 kHz)
XT
f
XX
WM
WM7 WM6 WM5 WM4
XX
= 4.194304 MHz and f
Selector
(32.768 kHz)
f
W
Internal Bus
Fig. 5-3 Watch Timer Block Diagram
8
WM3
f
XT
16
W
WM2 WM1 WM0
= 32.768 kHz are indicated in parentheses.
(2.048 kHz)
Frequency Divider
Clear
2
f
W
7
(256 Hz : 3.91 ms)
P23
Output
Latch
PORT2.3
0.5 sec
f
2
W
2Hz
14
Selector
Port 2
Input/Output
Mode
Output Buffer
Bit 2 of PMGB
PD75212A
INTW
IRQW
Set Signal
P23/BUZ