+; 6522
+.struct VIA ; Versatile Interface Adapter
+ .res $0300
+PRB .byte ; Port Register B
+PRA .byte ; Port Register A
+DDRB .byte ; Data Direction Register B
+DDRA .byte ; Data Direction Register A
+T1 .word ; Timer 1
+T1L .word ; Timer 1 Latch
+T2 .word ; Timer 2
+SR .byte ; Shift Register
+ACR .byte ; Auxiliary Control Register
+PCR .byte ; Peripheral Control Register
+IFR .byte ; Interrupt Flags Register
+IER .byte ; Interrupt Enable Register
+PRA2 .byte ; Port Register A without handshaking
+.endstruct
+
+; 6551
+.struct ACIA ; Asynchronous Communications Interface Adapter
+ .res $031C
+DATA .byte
+STATUS .byte
+CMD .byte ; Command register
+CTRL .byte ; Control register
+.endstruct
+
+SCREEN := $BB80