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The TPI 6525 is a chip with three I/O ports (Tri-Port-Interface). One of the ports can double as an interrupt prioritizer. Therefore we also have to save the states of the interrupt stack etc.
Version numbers: Major 1, Minor 0.
Type | Name | Description |
BYTE | PRA | Port A output register |
BYTE | PRB | Port B output register |
BYTE | PRC | Port C output register (doubles as IRQ latch register) |
BYTE | DDRA | Port A data direction register |
BYTE | DDRB | Port B data direction register |
BYTE | DDRC | Port C data direction register (doubles as IRQ mask register) |
BYTE | CR | Control Register |
BYTE | AIR | Active interrupt register |
BYTE | STACK | Interrupt stack - the interrupt bits that are not (yet) served. |
BYTE | CABSTATE | State of CA/CB pins. Bit 7 = state of CA, Bit 6 = state of CB |