From BASIC-G MANUAL [ 1983/3 ].

I/O PORT

Z80CTC

00h
Channel #1: SIO Int.
Channel #1: Peripheral Timer
Channel #2: SIO Clock Generator
Channel #3: VDP Blnaking (Frame) Interrupt

VDP TMS9918A

11h
Status port
Screen base address & Control port
VRAM Address port
Data Read port
Data Write port

Sound Generator SN76489AN

20h
Control

Keyboard

30h
Row#0
row#1
row#2
row#3
row#4
row#5
row#6

Joypad/Attack switch

37h
Joypad Direction Input

RESET/HALT key

50h
Reset/Halt Key data port (Bit 7)

Cassette tape recorder

50h
Output port (Bit 0)
Input port (Bit 0)
Remote port (Bit 1)

Pararrel Out

40h
DATA
STROBE (Bit 0)
BUSY (Bit 1)