84PCE:Ports:0000 Unknowns

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If a port is not listed; it indicates that writes have no effect and do not latch, and that reads are 0. Note that this may not be true one hundred percent.

0000 Range

Port    Default    Bits    Information   
0000 03 D3 Upper nibble's functions are unknown
0001 03 13 Bit 4's function is unknown
0002 ?? Read only, value can change
0005 76 ?? Set bit 5 to freeze, bit 6 affects backlight
0006 03 03? Reset bit 1 to disable display refresh
0007 B7 FF Reset bit 1 to cause crash after ? 1 second
0008 7F ?? Cannot change value
0009 ?? Appears to be a part of the power control system.
000A 05 ?? Latches value written, OS reset to 05
000B FC ?? Cannot change value
000C 00 FF Latches value written
000D FF FF Bit 0: Freeze if reset
Bit 1: Crash if reset
Bit 2: No apparent effect if reset
Bit 3: Reset to disable VRAM? Upon set, VRAM is garbage.
Bits [7:4]Possibly last value written
000E 0A FF Latches value written
000F 42 ?3 High nibble may be a status, low 2 bits latch value written
001C 80 ?? Cannot change value
0028 FD Bit 1 is always 0, other bits latch value written
0029 00 01 Bit 0 latches value written
002A 70 73 Latches value written
002B FE FF Latches value written
002C FF Ports 002C-0031 latch value written
0032 07 Latches value written
0033 F1 Latches value written
0034 31 Latches value written
0035 3F Latches value written
0036 FF Ports 0036-0039 latch value written