80-Bus News


July–August 1983 · Volume 2 · Issue 4

Page 17 of 55

Doctor Dark’s Diary – Episode 17.

When issues 2 and 3 of 80-BUS News arrived together, a friend of mine commented, “Just like busses! You wait months, and then they all come along at once…” I bet he wasn’t the only one to think that either! I only mention this because I think it is about to happen again. And all to save money on postage! [Ed. – Believe what you want!]

Whatever happened to… Part 94.

Readers of another magazine called Micropower may be wondering what happened to their “Win a CMOS RAM board competition”. So am I. I entered the competition, and sent suggestions for five boards that I thought would be good ideas. The results of the competition have yet to appear, although they have been due for a long time, as indeed their magazine has been, but I thought you might like to have a look at what I said to them. It was more or less as follows, except that I have edited in a few extra remarks, not just to protect myself from accusations of breach of their copyright on my material, but also because I have thought of them since the competition, and they make the boards even more desirable…

The 80-BUS is particularly well suited to the use of intelligent peripheral boards, a prime example of the species being the Pluto graphics board, which has a specification not very different from that suggested for a graphics board in one of the early episodes of “Doctor Dark’s Diary”. One of the main features of such a board is that it is accessed through the Z80 port addressing system, so that it does not take up any of the system’s memory space. I have five proposals for new 80-BUS boards, all of which would be of this type. As far as the main processor in the system is concerned, each of these boards would be controlled by the use of two or more ports, in much the same way as the Pluto and Gemini IVC boards are. One port is called the “status” port, and is used to find out whether the board is ready to receive fresh instructions or not; the other port is the “data” port, and the instructions and data are sent to this port. The five boards I propose are as follows:–

Intelligent speech generator.

This board would contain the following items:–

  1. Port decoding for two ports.
  2. A Z80 CPU.
  3. Random access memory.
  4. Read only memory.
  5. A Votrax SC-01 speech synthesis chip.
  6. Audio output circuitry.

The functioning of the board would be as follows. The main system processor would send codes representing the words to be spoken to the data port of the board. The on-board Z80 would store the instructions sent to it in the random access memory; the control program telling it how to do this would be stored in the ROM. During the periods when it was not reading the data port, which would be most of the time, the Z80 would control the SC-01 chip. The software in the ROM could be quite simple, providing only the necessary data collecting and speech control functions, or could include software to translate from normal text to the phonetic code required by the SC-01. If there was enough ROM, it would be possible to provide a dictionary of commonly used words, with their phonetic equivalents.

Page 17 of 55