84PCE:Ports:Control

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Synopsis

Port Number: 0000-0fff

Function: Master Control

This port range is used to configure and control important things; possibly the reason why it does not have a memory-mapped address. It is mirrored every 0x100 bytes.

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.

Port Address Space

Port    Default    Information   
0000 03 OS Timer Control
0001 03 CPU Speed Control
0002 Read only, value can change
0003 00 Hardware ID
0005 76 Set bit 5 to freeze, bit 6 affects backlight
0006 03 Display refresh
0007 B7 GPIO A DIR
0008 7F GPIO A IN
0009 37 GPIO A OUT
000A FD GPIO B DIR
000B F8 GPIO B IN
000C 00 GPIO B OUT
000D FF Power control
000E 0A Latches value written
000F 42 High nibble may be a status, low 2 bits latch value written
001C 80 Cannot change value
001D A7 Privileged address
0020 7C Memory protection
0028 Bit 1 is always 0
0029 00 Bit 0 latches value written
002A 70 Latches value written
002B FE Latches value written
002C Ports 002C-0031 latch value written
0032 Latches value written
0033 Latches value written
0034 Latches value written
0035 Latches value written
0036 Ports 0036-0039 latch value written