OSCILLATOR CIRCUITS KS57C2308/P2308/C2316/P2316
6-6
++ PROGRAMMING TIP — Setting the CPU Clock
To set the CPU clock to 0.95 µs at 4.19 MHz:
BITS EMB
SMB 15
LD A,#3H
LD PCON,A
INSTRUCTION CYCLE TIMES
The unit of time that equals one machine cycle varies depending on whether the main system clock (fx) or a
subsystem clock (fxt) is used, and on how the oscillator clock signal is divided (by 4, 8, or 64). Table 6-2 shows
corresponding cycle times in microseconds.
Table 6-2. Instruction Cycle Times for CPU Clock Rates
Oscillation
Source Selected
CPU Clock Resulting
Frequency Cycle Time (µs)
fx = 4.19 MHz fx/64 65.5 kHz 15.3
fx/8 524.0 kHz 1.91
fx/4 1.05 MHz 0.95
fxt = 32.768 kHz fxt/4 8.19 kHz 122.0