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

Emailing: CP-M Z80 home brew computer circuit board.htm bfranchuk at jetnet.ab.ca bfranchuk at jetnet.ab.ca <mailto:cctalk%40classiccmp.org?Subject=Emailing%3A%20CP-M%20Z80%20home%20br ew%20computer%20circuit%20board.htm&In-Reply-To=4855CBD5.9050403%40bellatlan tic.net> Tue Jun 17 11:09:33 CDT 2008 * Previous message: Emailing: CP-M Z80 home brew computer circuit board.htm * Next message: Emailing CP-M Z80 home brew computer circuit board * Messages sorted by: [ date ] [ thread ] [ subject ] [ author ] ________________________________ Allison wrote: I never could run the CP/M system I was using for more than 30 minutes with out the floppy stepper sticking. That was fun working with it. Still how do you transfer stuff from a floppy ( or file online ) to a CP/M system with no external I/O devices? That I would like to see. I still am using paper & pen. Mind you I have to buy JAPANESE pens since the quality of the USA stuff is all cheap Chinese imports. Now that I have a serious cad program - DIPTRACE on order I think I will put the design in hardware. I got that covered if I read the 2901 data sheets correctly. I will be using a 6809 style memory cycle optimized for D-RAM access and clock the 2901 in 4th phase of the memory cycle. This is retro computing project for the feel of the late 1970's not using a 8 bit CPU. I am aming for a 800ns memory cycle and the slow access of micro-code is not a problem. The only thing pipelined is the next memory cycle - Read/Write/Refesh and the default is refresh while doing the the 1st cycle of op-code decoding. The front panel does RUN/STOP, Single Instruction,Address Load, Deposit,Read. -----REPLY----- Hi, I can answer the question on how to get programs and data into and out of the SBC. There are three ways with the basic SBC; 1) XMODEM at the CP/M prompt 2) Intel Hex format transfer at the RAM Monitor prompt and 3) burn your own EPROM with the supplied image or your own custom disk image (utilities are on the website) Here is a little background on the N8VEM SBC design principles The N8VEM SBC is meant to be flexible and low cost. If you start with the PCB only, you can minimize cost by not installing unneeded functions such as; 1) RTC 2) 8255 PPI and parallel port connector 3) ECB Bus transceivers and DIN 41612 connector You can also substitute some parts to reduce cost. Replace the 1Mx8 EPROM with a 128Kx8 27C1001 is a drop in replacement. Scrap and salvaged parts can be used directly or with minor modifications. All the chips are commonly available plain TTL and can be substituted. All of the other components can be substituted if you know what you are doing. Scrap 29C020 Flash ROM chips (PC BIOS) can be reused with a simple shim socket. Most likely 128Kx8 SRAM parts with a shim socket can be used but I haven't tested it yet Installing and running CP/M 2.2 OS is strictly a convenience and an option. Any generic CP/M application should work. The RAM and ROM drives are lightning quick and silent. You'll never see a hung stepper motor with SRAM! The SBC boots into the RAM monitor so you may never need to run CP/M at all if you don't want to. The system I built is rock solid. It runs for hours doing things without a sound or glitch. I used some CMOS components so the SBC runs cool. Power supplies are easy and cheap. Use spare ATX/AT PS or your own with the common Molex drive connector. Of course, all the hardware and software details are fully published and with datasheets for all the components. Except for the EPROM there are no custom or programmed devices at all. All components are bog standard common 74LSxxx TTL and LSI peripherals. It is designed to be built with low cost tools and simple test equipment such as 25W soldering iron and VOM. EPROM programmer, logic probe and/or oscilloscope are useful but optional. You can easily write your own replacement software like a FORTH kernel or custom Z80 boot code if you'd like. The EPROM on the N8VEM site is strictly optional and I actually discourage people from using the pre-programmed part. Write/burn your own and save $$$ on construction. With the low cost PCB available and using standard low cost components anyone can build their own SBC for low cost. You can add the features you like later on and even expand the system via the ECB to be a full blown microcomputer. Once a few of these systems get built "out in the field" I would like to start a challenge to see who can build an SBC for the least cost. Those with a well stocked junk box or access to scrap PC electronics would have an advantage of course. Compared to a design it yourself using wire wrap/prototype boards/breadboards, this SBC PCB will save you time and money on construction. Manufactured PCBs are also more reliable than temporary construction methods in the long term. It will be fun to make, useful, and educational. Thanks and have a nice day! Andrew Lynch