38
edits
Changes
→GPIO Initialization: Document PF6
51K resistor to ground
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|21
|47k pullup
U3 - Pin19
|Appears to be some sort of test-mode select, checked before GPIO initialization.
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|23
*PFDDR = 0x20 or 0x80 depending on address 0xF3, PFOR=0x10 or 0x80 depending on address 0xF3
**PF7 - depends on 0xF3
**PF6 - floating input- is checked very early on startup and used to set 0xF3. 47k resistor to 5v, TP8, CardEdge21.
**PF5 - depends on 0xF3
**PF4 - depends on 0xF3
**PF0 - floating input
=== MCC Initialization ===
Done in the main function, MCCSR is initialized to 0x0E. This means:
* Clock Prescaler[CP] is set to /2* SlowModeSelect[SMS] is set to 0, so CP is ignored and Fcpu=Fosc2* TimeBase[TB] is 0b11, selecting 25ms timebase* OscillatorInterruptEnable[OIE] is set, has something to do with low-power mode(s)* OscillatorInterruptFlag[OIF] is clear, indicates main oscillator has reached countdown
MCCBCR does not appear to be initialized, meaning beeper-mode is disabled.