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S3P80C5/C80C5/C80C8
CLOCK CIRCUITS
7-3
SYSTEM CLOCK CONTROL REGISTER (CLKCON)
The system clock control register, CLKCON, is located in set 1, address D4H. It is read/write addressable and
has the following functions:
— Oscillator frequency divide-by value
CLKCON register settings control whether or not an external interrupt can be used to trigger a Stop mode
release. (This is called the "IRQ wake-up" function.) The IRQ wake-up enable bit is CLKCON.7. In
S3P80C5/C80C5/C80C8, this bit is not valid any more. Actually bit 7, 6, 5, 2, 1, and 0 are no meaning in
S3P80C5/C80C5/C80C8.
After a reset, the main oscillator is activated, and the f
OSC
/16 (the slowest clock speed) is selected as the CPU
clock. If necessary, you can then increase the CPU clock speed to f
OSC
, f
OSC
/2, or f
OSC
/8.
System Clock Control Register (CLKCON)
D4H, Set 1, R/W
.7
.6
.5
.4
.3
.2
.1
.0
MSB
LSB
Divide-by selection bits for
CPU clock frequency:
00 = f
OSC
/16
01 = f
OSC
/8
10 = f
OSC
/2
11 = f
OSC
(non-divided)
Not used
Not used
Not used
Figure 7-4. System Clock Control Register (CLKCON)
Summary of Contents for S3P80C5
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Page 49: ...ADDRESS SPACES S3P80C5 C80C5 C80C8 2 20 NOTES ...
Page 197: ...INSTRUCTION SET S3P80C5 C80C5 C80C8 6 88 NOTES ...
Page 201: ...CLOCK CIRCUITS S3P80C5 C80C5 C80C8 7 4 NOTES ...
Page 237: ...TIMER 1 S3P80C5 C80C5 C80C8 11 6 NOTES ...
Page 245: ...COUNTER A S3P80C5 C80C5 C80C8 12 8 NOTES ...
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