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User:Trap15/fm7sub
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Sub RAM Physical Map
| Start | End | Detail |
|---|---|---|
| $0000 | $BFFF | GVRAM |
| $C000 | $CFFF | "Console" RAM Bankable on AV40 |
| $D000 | $D37F | "Work" RAM |
| $D380 | $D3FF | Shared RAM |
| $D400 | $D4FF | Memory mapped I/O |
| $D500 | $D7FF | RAM AV only |
| $D800 | $DFFF | Subsystem CG RAM Other than AV40, this is ROM |
| $E000 | $FFFF | Subsystem RAM Other than AV40, this is ROM |
Sub I/O Map
Address mask depends on machine. This table goes from most to least specific. If it's not covered, fall through.
| Machine | Mask |
|---|---|
| AV40EX/AV40SX | $FF |
| AV | $3F |
| Other | $0F |
| Address | R/W | Detail | |||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| $D400 | R | Keyboard data high bit
| |||||||||||||||||||||
| $D401 | R | Keyboard data low 8 bits
| |||||||||||||||||||||
| $D402 | R | Acknowledge IRQ from main CPU | |||||||||||||||||||||
| $D403 | R | One-shot buzzer | |||||||||||||||||||||
| $D404 | R | Send attention IRQ to main CPU | |||||||||||||||||||||
| $D405 | W | Sub-CPU mode
CSCP emulator implies this port interacts with the 400 line board config. | |||||||||||||||||||||