The 8259A on the PIC/RTC board can work in “status poll” mode with a Z80. The 8259A will not work (without some very tricky hardware circuits involving the chip itself, putting DMA states on the bus and modifying the Z80 board) with a Z80. This has to do with how Intel programmed the 8259A to responds to an INTA signal. (oversimplifying, it puts back on the bus two INT vectors). The Zilog chips expect one. Alternatively you could use the AMD’s 9519 where the number of returned INTS was programmable (1, 2 or 3). However both the Zilog and AMD chips are quite different in their software interface ( and not compatible with a generic MS-DOS disk). Thus the name “MSDOS support board”. Of course the above board will work fine with the 8086 etc. CPU’s The Z80 for and 8 bit CPU actually has a powerful interrupt structure. The S-100 PIC/RTC board actually allows it to be utilized. It is summarized here:- http://s100computers.com/My%20System%20Pages/PIC&RTC%20Board/My%20PIC%20Board.htm As to RTC, clearly no problem, it’s just a series of ports to the Z80. Though again the MSDOS support board utilizes a PC compatible RTC (local RAM) and timer. Hope the above helps. John From: n8vem...@googlegroups.com [mailto:n8vem...@googlegroups.com] On Behalf Of yoda This would be good for the 68K board if you want to do other than CPM 68K. Could be used in port of emuTOS and uCLinux - necessary for multi-tasking systems. On Tuesday, June 3, 2014 8:08:32 AM UTC-5, Edward Snider wrote: Are there many people interested in this board? If there is enough interest (20 boards) I can handle a run of these.
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