UPD75518 NEC, UPD75518 Datasheet - Page 67

• Manufacturer Part Number: UPD75518
• Description: 4 BIT SINGLE-CHIP MICROCOMPUTER
• Manufacturer: NEC

From the
clock
generator
4.5 CLOCK TIMER
(1) Clock timer
(2) Clock timer functions
Remark The values in parentheses indicates are for f
The PD75518(A) contains one channel for a clock timer. Fig. 4-22 shows the configuration of the timer.
(a) The clock timer sets the test flag (IRQW) every 0.5 seconds.
(b) Either the main system clock or subsystem clock can produce 0.5-second intervals.
(c) The fast-forward mode produces an interval 128 times faster (3.91 ms), which is useful for program
(d) A fixed frequency (2.048 kHz) can be output to the P23/BUZ pin, so that it can be used for sounding
(e) The frequency divider can be cleared, so the clock can start from zero seconds.
Caution
The standby mode can be released with IRQW.
debugging and testing.
the buzzer and system clock frequency trimming.
(32.768 kHz)
f
(32.768 kHz)
128
XT
f
X
When the main system clock operates at 6.0 MHz, a time interval of 0.5 s cannot be produced.
Before producing this time interval, the main system clock must be changed to the subsystem
clock.
WM
WM7
0
Selector
0
Fig. 4-22 Block Diagram of the Clock Timer
f
(32.768 kHz)
W
0
8
0
16
f
W
WM2 WM1 WM0
(2.048 kHz)
Frequency divider
Internal bus
X
= 4.194304 MHz and f
Clear signal
f
2
W
7
(256 Hz: 3.91 ms)
P23 output
latch
2
PORT2.3
f
2 Hz
0.5 sec
W
14
XT
= 32.768 kHz
Selector
Port 2 input/
output mode
PD75518(A)
Output buffer
Bit 2 of PMGB
INTW
IRQW
set signal
P23/BUZ
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