Watford Electronics A3000 BBC User I/O
The card is intended for the internal expansion slot in machines such as the A3000, A4000, A3020 and A3010. The card basically offers an 8-bit Input/Output (I/O) port together with a 4-channel analogue to digital converter. The I/O card can therefore be used to control external devices (with additional hardware), or indeed to monitor the surroundings (again, extra hardware and/or transducers may be needed). Software written in BASIC for the BBC Micro will work with this card providing the legal SYS (from BASIC), SWI (from Assembler) or OSBYTE calls have been used.
The I/O port is port "B" of a 6522 VIA, and so offers eight I/O lines plus control lines CB1 and CB2. The pin-out on the back of the card is exactly the same as the "user port" on the bottom of the original BBC Micro. Each of the eight I/O pins can be set in software to be either an input or an output, in any combination.
On the analogue side, the four input channels are obtained from a uPD7002 chip, again as supplied with the BBC Micro. In addition to the user port and A/D converter described above, there is also an inter-IC (I2C) bus present.
The Watford Electronics BBC A3000 I/O Card User Guide is available HEREDate : 1991
Manufacturer : Watford Electronics
Physical Description : Expansion board
This exhibit has a reference ID of CH48133. Please quote this reference ID in any communication with the Centre for Computing History.