SN8P1602B
8-Bit Micro-Controller
External RC Oscillator Frequency Measurement
There are two ways to get the Fosc frequency of external RC oscillator. One way is to measure the XOUT output
waveform. Moreover, the other way is to measure the external RC frequency by software instruction cycle (Fcpu).
ꢁ
Example: Fcpu instruction cycle of external oscillator
B0BSET
P1M.0
; Set P1.0 to be output mode for outputting Fcpu toggle signal.
@@:
B0BSET
B0BCLR
JMP
P1.0
P1.0
@B
; Output Fcpu toggle signal in low-speed clock mode.
; Measure the Fcpu frequency by oscilloscope.
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Note: Do not measure the RC frequency directly from XIN, the probe impendence will affect the RC
value.
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