The Digital Model Train Part 7

THE DIGITAL MODEL TRAIN PART 7 by T. Wigmore The seventh part in the series deals with the circuit description of the main unit in the Elektor Electronics Digital Train System. The construction and testing will be the subject of next month"s instalment. The main unit consists essentially of a sin- gle-board processor system based on a Z80 as shown in Fig. 47. This processor was chosen not only for its very low price, but also because the special Z80 peripheral chips (Pio - parallel input/output - and crc - counter timer control) make it possi- ble to use the powerful Z80 interrupt struc- ture without the need of additional logic. Since the train system requires a number of asynchronous processes to be carried out more or less simultaneously, this is a very worthwhile aspect. Apart from the standard Z80 design, consisting of the processor proper, memo- ries and a crc for general timing functions, the unit also contains various i/o struc- tures. Reading of the locomotive contr...