Nascom News­let­ter

19. user.
20. 2K bytes of CMOS static RAM are addressable via the I/O ports resident on the stereo sound generators. A re-chargeable battery can be included to power the RAM during shut-down, hence, the RAM is effectively non-volatile.
21. The CMOS RAM chip enable line is protected against switch on/off transients with power up/down mute circuitry to avoid corruption during the initialisation and powering down operation.
22. Two real-time clocks are laid out an the board to permit the choice of one of to manufacturers. Both clocks are accessed via one sound generator’s I/O ports and are powered from the on-board battery, hence time, together with a calendar, are constantly available to the user.
23. If the Mullard clock IC is used, an alarm line is brought out to a plug and can be used to bring the system out of standby at any required time or date.

These are the main features of the board and they all combine together to give the Nascom user all those twiddly bits that aren’t present on a standard Nascom.

Construction of the board is quite straight forward once you have made sure that all the track pins are in. The board can be built up in stages once the port I/O has been added along with the buffering. This means that it can be used solely as a video board or sound board, etc and the other parts added as and when needed. All the chips are reasonably easy to get hold of. A list of suppliers of the ‘rarer’ chips is supplied with the documentation to make things easier. The most expensive chip is the video chip at about £30 and to populate the complete board costs in the region of £70 which means that to add all the above features to your Nascom will set you back by between £95. and £100 which can’t be bad. Some savings can be made by using a less accurate A-D converter. The one specified costs around £8 but for most uses the less accurate version at about £2 will suffice.

Programming the board is reasonably straight forward but it does involve sending everything through the ports. Routines to provide easy port and chip register access are pretty essential to make the most of the board.

All an all the board is very good and value for money it has to be bargain of the year. The main feature that I would like to have seen included on the board would have been some circuitry to provide a directly useable colour output, either ready for a colour TV or colour monitor. Bar this though, I do not think that the board can be faulted. Well worth the money.