I/O Map
The following table lists the main I/O definitions of the VP3301.
| EF1 | Display / Non display period |
| EF2 | CTRL key |
| EF3 | SHIFT key |
| EF4 | UART Interrupt (reversed) |
| OUT 1 | Load UART control register |
| OUT 2 | Load UART transmitter register |
| OUT 3-7 | 1870 OUT 3 to 7 |
| INP 1 | Read UART status register |
| INP 2 | Read UART receiver register |
| INP 4 | DIP switch bit 0 - Character set, 0:+ Uppercase and lower case, 1: Uppercase only bit 1 - Number of bits, 0:+ 8 bits, 1: 7 bits bit 2 - TBC, E/M / O/S Parity - even/mark or odd/space bit 3 - Stopbits, 0:+ 1 SB, 1: 2 SB bit 4 - local echo, 0: ON, 1:+ OFF bit 5 - Control codes, 0: OFF, 1:+ ON bit 6 - TBC, CD / OFF Carrier detect on/off bit 7 - Screen size, 0: 20x12, 1:+ 40x24 |
| Address 0x8000 | Read: key input Write: set row |