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 <http://s100computers.com/My%20System%20Pages/PIC&RTC%20Board/My%20PIC%20Board.htm> &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: [email protected] [mailto:[email protected]] On Behalf Of yoda Sent: Tuesday, June 3, 2014 7:02 AM To: [email protected] Subject: [N8VEM-S100:3928] Re: S-100 PIC/RTC Board Production 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 8:57:00 AM UTC-5, Vince Mulhollon wrote: 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. My interpretation of the board is its a non-msdos compatible msdos support board. I'm curious if there's any software, features, compatibility, advantages of this specific board. So the XYZ board only works with the PIC/RTC board and not the MSDOS support board because of ... They are both basically 8259 plus a RTC, right, I think? And the msdos board adds the keyboard hardware and msdos timers, right? I'm unclear on this and that would help me figure out if I want one of these. -- You received this message because you are subscribed to the Google Groups "N8VEM-S100" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "N8VEM-S100" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
