John, can you please elaborate on how you have implemented the two banks for banked CP/M3 on the SBC? In a previous email, you mentioned somehow using A16, but I wasn’t following how you were synthesizing A16, as it doesn’t exist on the Z80. Do you have an I/O port somewhere that will drive A16? And do you have an algorithm in mind for how you would switch banks to be implemented in CP/M BIOS function 27 (SELMEM)? Thanks. Bob Bell From: n8vem...@googlegroups.com [mailto:n8vem...@googlegroups.com] On Behalf Of John Monahan Hi Tom, Normally I would agree and these days I’m a GAL/CPLD convert. But I’m thinking that since this may be the very first S100 board a new user may build I would like to keep the variables/challenges to a minimum. The board is linked 100% with simple 74LSxx chips. The circuits are such that I should be able to write-up fairly straightforward build and debug steps on the web page – explaining what each sub-circuit does. I kind of intend to go overboard on the board build/debug for this one to help first time users get airborne. I continuously get e-mails about “chicken & egg” problems with users getting started in hardware. With this board they should later be able to step by step inactivate sections and go on to build more powerful multiprocessor systems. Where I will need help is not only some of you double checking the write-up (when it’s done) but I really could use support in doing a CF-Card image downloaded from a PC that will immediately allow booting up a banked CPM/3 system. I really could use one or two volunteers for this. The end goal being:- built a board, pop in that CF card, hook up a Telnet PC USB connection over your laptop and you instantly have a running S100 bus CPM system. BTW, I managed to get Freerouter to get me a board with only 520 vias. Will send off to Advanced Circuits for prototype tonight. FYI here is a picture of the board layout, . |