John... Use the GALS... Save board space, just make the parts available withe the board as an option...
i~~ _/) ~~~~ _/) ~~~~ _/) ~~~~ _/) ~~i Tom Lafleur (858) 759-9692 > On Sep 11, 2015, at 7:06 PM, John Monahan <[email protected]> wrote: > > Thanks everybody for the suggestions. > Here is what I’m currently going with and why… > > First and foremost I wanted a Z80 circuit that is proven and works with > almost every vintage s100 board out there. I used the core circuit on our > Z80 board > (http://s100computers.com/My%20System%20Pages/Z80%20Board/Z80%20CPU%20Board.htm > ). It’s based on the old Intersystems II CPU board. I have not come across > a vintage S100 board it does not work with. It goes to 10MHz in my own system > of mainly S100Computers boards. Even works with DRAM boards. I had to remove > the >64K windowing circuit for board space (see below). The Z80 to S100 bus > signal conversions take up quite a few 74LSxx chips. Granted that could be > reduced with a GAL or two but newcomers will probably not have experience > programming GAL’s initially. > > Second, I brought in the circuit from the Propeller Console IO board > (http://s100computers.com/My%20System%20Pages/Console%20IO%20Board/Console%20IO%20Board.htm > ). Because of space I removed the HEX display and a few jumpers. This > provides direct support for PS2 keyboard and VGA video. Besides the internal > ribbon cable connectors to the back of a box, I also added IBM-PC P2 and VGA > sockets at the top of the board for direct connections. Again my thinking > was KISS. It’s a well proven board totally debugged and is completely > programmable (currently has VT100 capability as well). I wanted to retain > the flexible status port and bit configuration jumpers section so when > sections are disabled to use an external board (see below) the monitor need > not be. Granted there is a simpler solution such as the PIC32. I may have to > go to that for space reasons but with the Propeller circuit 99% of the work > is done it’s just a splice. Also later, the user can get and use the > Propeller Console IO easier when they build a larger system. The interrupt > circuit is still there BTW. > > There was an outcry for a serial port. These unfortunately take up board > real estate badly. I opted to add the (again well proven) USB port chip that > we used on our Serial I/O board > (http://s100computers.com/My%20System%20Pages/Serial%20IO%20Board/Serial%20IO%20Board.htm > ). This 18 pin “chip” takes up little circuit room and actually is easier > to interface to a PC than a serial port. USB the serial cables are also very > common. > > Added a few LED’s that’s about it. > > The board has 128K of RAM (there are no common 64Kx8 static RAM DIP chips) > that can be jumpered into two separate 64K sections. It has a 27C64 (or > equivalent) ROM, keyboard buzzer, 8 interrupt jumpers, a Power on clear and a > ROM power on jump to any 1K boundary circuit. I used two, a 5V and 3.3V > Pololu regulators. There are a lot of chips on this board. A TO-3 regulator > capable of > 1.5 Amps takes up too much space. Those Pololu units are really > nice and take little real estate. > > There is a socket to program the Propeller EEROM but the user will have to > buy the “Propeller Programming Plug”. A serial interface circuit is too > board space expensive. They would also need to buy a PROM/EEPROM programmer > (e.g. Wellon VP-290). After that they should have a board that would light > up an empty S100 bus card cage. Clearly the next thing to do would be to > build a FDC board or IDE/CF Card board and then go from there… > > The circuits are configured so the onboard RAM, ROM, Console I/O and serial > sections can be inactivated in stages as discrete more functional boards are > added. While the board will act as a master/slave S100 board it’s not really > intended to function is a complex multiprocessor configuration. For example > for debugging you cannot “see” beyond 64K of RAM in the bus. > > A few of you wanted more options including a CF card etc. Unless we went > with a 4 layer board (more expensive, hard to debug), there is unfortunately > not enough room. GAL’s (or a CPLD) would help but I wanted to simplify the > board for first time users. The current 74LSxx board is amenable to simple > logic probe debugging in all the circuits. > > Now the bad news. This board is very dense. The initial via count is ~1200 > vias! (More in fact than my current 80486 CPU prototype boards). It’s taxing > Freerouter to find a solution. I playing around with chip layouts. May need > some volunteers to shuffle things around an try for a solution. The multiple > jumper options really soak up vias. > > Anyway stay tuned. > > John > > > > > > > > > From: [email protected] [mailto:[email protected]] On > Behalf Of Richard Cini > Sent: Friday, September 11, 2015 3:09 AM > To: [email protected] > Subject: Re: [N8VEM-S100:7551] Re: A new Z80 based SBC to get beginners > started on the S100 bus > > On Phillippe's second point, the DSKY already exists for the N8 ECB platform > so maybe you can reuse that? > > I forget -- would the proposed board have a parallel port or two? That'd be > great for a parallel ascii keyboard. > > Sent from my iPhone > > On Sep 11, 2015, at 1:51 AM, Philippe Elie <[email protected]> wrote: > > Hi all, > > I'm jumping in this thread a bit late, it's a great idea John! I was > considering building a Zeta SBC but was missing the S100 compatibility. The > board you suggest could be used not only for diagnostic but also to build a > compact S100 system based on a 4-slot backplane for example. > > a couple of comments : > - also agree that serial is essential, video not that much. Propeller is > great but, having spent quite some time tweaking the code, there are inherent > limitations when running DOS as several programs are addressing the video > memory directly and this makes it quite difficult to emulate. as such, we > should rather leave the video chip decision to the user and integrate the > serial port only. > - I own several old school SBCs, as I guess several people here, KIM1, SYM1, > TM990 etc and one feature they all have which is neat is a tiny hex keyboard > and LED digits. I was wondering if this very limited entry/display device > would also be included in the board, probably via a dedicated connector and > external daughter board.. that would make debugging, patching, etc quite > straightforward, and helping in situations where an external serial terminal > cannot be used > > my 0.002 cents ! > Philippe > -- > 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. > -- > 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. 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