Internal Port Decoding b0-7 Register
| Number | TBRegisterNumber::$82 |
|---|---|
| Readable | TBRegisterReadable::Yes |
| Writable | TBRegisterWritable::Yes |
| Short Description | ShortDesc::Enabling internal ports decoding |
| Bit | Description |
|---|---|
| 7 | Enabling {{#ask:
PortNumber::$xx37 }} ($xx37{{#ask: PortNumber::$xx37 |mainlabel=- |headers=hide |intro= / |?NumberDec#- }}) (also MD2 controller) |
| 6 | Enabling {{#ask:
PortNumber::$xx1F }} ($xx1F{{#ask: PortNumber::$xx1F |mainlabel=- |headers=hide |intro= / |?NumberDec#- }}) (also MD1 controller) |
| 5 | Enabling {{#ask:
PortNumber::$xx6B }} ($xx6B{{#ask: PortNumber::$xx6B |mainlabel=- |headers=hide |intro= / |?NumberDec#- }}) |
| 4 | Enabling +3 floating bus |
| 3 | Enabling {{#ask:
PortNumber::$1FFD }} ($1FFD{{#ask: PortNumber::$1FFD |mainlabel=- |headers=hide |intro= / |?NumberDec#- }}) |
| 2 | Enabling {{#ask:
PortNumber::$DFFD }} ($DFFD{{#ask: PortNumber::$DFFD |mainlabel=- |headers=hide |intro= / |?NumberDec#- }}) |
| 1 | Enabling {{#ask:
PortNumber::$7FFD }} ($7FFD{{#ask: PortNumber::$7FFD |mainlabel=- |headers=hide |intro= / |?NumberDec#- }}) |
| 0 | Enabling {{#ask:
PortNumber::$xxFF }} ($xxFF{{#ask: PortNumber::$xxFF |mainlabel=- |headers=hide |intro= / |?NumberDec#- }}) |
since core3.1.1: all bits are set to 1 when: soft reset and bit 31 is set OR hard reset and bit 31 is clear (otherwise content is kept intact). All bits are set to 1 upon soft reset.
The internal port decoding enables always apply.
When the expansion bus is on, the expansion port decoding (Next Registers $86-$89) enables are logically ANDed with the internal enables (Next Registers $82-$85). A zero bit indicates the internal device is disabled.
If the expansion bus is on, this allows I/O cycles for disabled internal ports to propagate to the expansion bus, otherwise corresponding I/O cycles to the expansion bus are filtered.
(note: Next registers with number higher than $7F are inaccessible from Copper code)