Entrex/Nixdorf "Trapezoid" Terminal theories of operation & Testing

;IOMAP

;0x40 INPUT        read from ram expansion card (tbd)

;0x40 OUTPUT       poke at FDC (tbd)

;0x48 INPUT        read the key modifier bits (i assume) from keyboard, and the key pressed latch bit

;0x48 OUTPUT       (unused in ROM) alternate poke at FDC

;0x50 INPUT        read the keyboard state and clear they key ready latch

;0x50 OUTPUT       tough to see from the schematic, seems to toggle an unconnected port, could be a feature we dont have?

;0x58 OUTPUT       write to interface card register high

;0x60 OUTPUT       write to interface card register low

;0x68 INPUT        read from interface card buffer

;0x68 OUTPUT       something to do with transmit (previously predicted this as transmit byte)

;0x70 INPUT        read the interface card "printer status" register

;0x70 OUTPUT       something to do with transmit (tbd)

;0x78 INPUT        read the interface card status register

;0x78 OUTPUT       write status to interface card