Emailing CP-M Z80 home brew computer circuit board.htm

Emailing CP-M Z80 home brew computer circuit board.htm Eric Smith eric at brouhaha.com <mailto:cctalk%40classiccmp.org?Subject=Emailing%20CP-M%20Z80%20home%20brew% 20computer%20circuit%20board.htm&In-Reply-To=2A5D64469F2B4C2AAF06BA09719DFB0 1%40andrewdesktop> Tue Jun 17 18:19:21 CDT 2008 * Previous message: Emailing CP-M Z80 home brew computer circuit board.htm * Messages sorted by: [ date ] [ thread ] [ subject ] [ author ] ________________________________ Andrew wrote: I have yet to see a CP/M system with no external I/O devices. That doesn't sound very useful, so why would one care about transferring stuff to it? Eric -----REPLY----- Hi, Who said the N8VEM SBC has no external devices? The SBC has some self contained memory drives but supports external devices over the ECB. The SBC supports a RAM drive (448K B:) and two ROM drives (32K A: and 992K F:) internally. The CBIOS *currently* (read the CBIOS source) supports IDE interface and three hard disk partitions (8M C:, 8M D:, 1M E:) via the Disk IO board. I know the 8M C: drive is fully functional since I have one on my workbench. You can transfer temporary files in and out of the system using the serial line into the RAM drive or burn them into EPROM. The data is available on each device exactly the same except ROM drives are RO and the RAM drive is RW. CP/M CBIOS treats them as block devices and from an operators view they are identical to disk drives. Were there floppy disk with the same DPB as the ROM, the ROM image would also work as a disk image. I do not see why someone who wanted to couldn't write a serial based block device in CP/M and treat the host PC as a block device disk drive. It is of no real interest to me but the modifications to the CBIOS would not be all that hard. You'd also have to write an application on the PC side to handle the serial IO block servicing and with the terminal emulation. It'd be tedious but probably not too difficult. For me XMODEM works just fine to transfer any files to/from the PC as needed. I also do a lot of work off target on the PC and transfer the final binary image to the SBC for testing. The SIMH simulator supports an N8VEM mode I use a lot for development and test (Thanks Howard!) The IDE interface requires the Disk IO board which I have on my bench as a prototype built with prototype cards. The schematics/CBIOS source are available if you'd like to build one too. It also includes a NEC 765 based floppy controller interface. The IDE interface works for sure as I used it for quite a while. The floppy interface is built but never fully tested. My prototype board based system started having problems with reliable grounding when I took a break to work some other projects. The next project is to make an ECB backplane and then a bus debugger from my existing prototypes. After that, recraft the Disk IO board as manufactured PCB. The first thing I did when I restarted the project is begin the conversion of prototype boards to manufactured PCBs. Compared to my original prototype computer, the new manufactured PCB SBC is MUCH more reliable and easier to build. If there are enough units out there to make it worthwhile, I may order several manufactured PCBs for other hobbyists. If not, I will probably just go with another small run of barebone prototype boards for the rest of my boards. I did a run of two SBC prototype PCBs to verify the design before I did this latest run of manufactured PCBs. As for CP/M, you are not REQUIRED to use it. Write your own stuff and burn your own EPROM. However, a plain Z80 SBC is perfectly useful without CP/M. CP/M is just an operating system. CP/M works fine loading and running programs from the RAM/ROM drives however you could just as easily just use the RAM monitor. Better yet, write your own kernel and application. Whatever you like. I split my usage about 50% between the monitor and CP/M. Home brew computers are *not* all nicely finished and debugged so it magically does everything want when you plug it into a wall. That is what makes them a challenging and an enjoyable hobby. People who take it on should expect to get their hands dirty. If you are expecting a pristine flawless commercial product then this project is not for you. Thanks and have a nice day! Andrew Lynch