Re: HP 35s (and 42s) Crystal replacement Message #2 Posted by DaveJ on 8 Jan 2008, 5:22 a.m., in response to message #1 by Lyuka
Quote:
Reacentry I got some cylindrical crystal resonator of 65.536kHz.
Then tried to replace the crystal of the HP 42s and 35s.
Overclocking 42s is successful, however,
hp35s seems strange.
If the frequency of the crystal does not affect the calculation speed, what is the use of the crystal? What is clocking the MPU, I wonder?
This has been answered in previous threads.
The 32.768KHz watch crystal in the 35S is only for the Real Time Clock (RTC) function. The main oscillator is an RC type, the frequency of which is set by a single external resistor (internal capacitor).
The main oscillator frequency can also be software controlled with various divider ratios. So there will be a register in the processor somewhere where you could also change the frequency.
Check the Sunplus processor datasheet for details.
Dave.
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