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9.2.2.8 TPI module

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.

TypeNameDescription
BYTEPRAPort A output register
BYTEPRBPort B output register
BYTEPRCPort C output register (doubles as IRQ latch register)
BYTEDDRAPort A data direction register
BYTEDDRBPort B data direction register
BYTEDDRCPort C data direction register (doubles as IRQ mask register)
BYTECRControl Register
BYTEAIRActive interrupt register
BYTESTACKInterrupt stack - the interrupt bits that are not (yet) served.
BYTECABSTATEState of CA/CB pins. Bit 7 = state of CA, Bit 6 = state of CB