27-04-2021, 10:39 AM
(25-04-2021, 08:38 AM)gentle1 Wrote: I Haven't come across the DG750 I/O card if you have any info I would be interested in having a look at it.
The repository only contains a summary of the board thus someone has tried to contact David Griffiths for more information but until successful all that can be said is that it consists of:
4 x Signetics 2561/2662 USARTs
2 x 8255 PPIs
2 x AM9519 Programmable PIC controller (How many persons actually had or used the DG 680 CPU's PIC or SWP RAM?)
Someone has used Z80 SIO/DARTs and the subsequent SCC for some of their designs because it more easily works with the Z80 daisy chained interrupt hardware. In the 1970's & 80's the Z80 SIO, DART, DMA and some other peripheral ICs were frightfully expensive.