Technical Reference Material

Here are some useful links to other technical resources:

H8 Emulation Help — This is the complete help system that is distributed with the emulator, which includes:

• 8080A technical reference;
• a complete HDOS API guide (e.g., Syscall documentation);
• extensive Benton Harbor Basic documentation;
• H-19 and printer programming documentation;
• a detailed memory map, including useful ROM entry points and system information in RAM;
• Heathkit-provided software operating documentation;
• emulator operations documentation;

...and a whole lot more.

The 8080A programming section includes a good summary of each machine instruction along with an octal opcode reference summary, so the one that used to be here has been removed.

Disclaimer: All but the most trivial code samples have been tested, and the text has been carefully reviewed, but mistakes do get through. After all, there is over half a meg of text and formatting here.

Also, note that this guide was formatted for the Macintosh help viewer. There may be (in fact, are!) some display problems here and there when viewing this material on a normal web browser. Such is life.

8080A Programming Card — This is a terse but comprehensive instruction summary. The format is ASCII text.

8250 UART Technical Details — The 8250 chip in detail, including hardware operation and software programming, from Dave Wallace's site. HTML format.

go to top

Other Heathkit Links

Here are some other Heathkit, H8 and other microcomputer links you might find interesting:

Heathkit — Yes, they're still out there! The website only shows their educational products, but I'm told that they still sell documentation and some parts. Call them for info.

Dave Wallace's H8 Emulator Page — Dave's H8 emulator is (a) targeted at Windows NT, and (b) up and running. The web site has interesting history of the H8 and hobby computing in general, with considerable technical background on the H8. His description of "virtual time" alone is worth the visit.

Vintage Computer Festival — "The mission of the Vintage Computer Festival is to promote the preservation of "obsolete" computers by offering people a chance to experience the technologies, people and stories that embody the remarkable tale of the computer revolution."

The Heathkit Virtual Museum — Dedicated to Heathkit radio products, though it does have a picture of an analog Educational Computer that was once marketed by Heathkit before even my time.

8-Bit-Nirvana — Sogar in Deutschland, moegen sie das H8.

Bill Wilkinson's Heath Company Page — Bill Wilkinsen's tribute to the Heathkit company and its products. Has a number of additional resources, including names and e-mail/web addresses of a number of the people in the Heathkit computing community.

In addition, you can get interesting information from the comp.sys.zenith and comp.sys.zenith.z100 Usenet newsgroups. And quite a bit of the information I gathered for this project came from folks who hang out at alt.folklore.computers. The H8 is old enough to have developed folklore... My my.

If you know of any other interesting Heathkit sites, and especially H8 sites, that I might add to this link page, please send them to me.

go to top

Credits and Contributions

This project would be a complete failure if it weren't for the help of a number of total strangers who responded to a plea blatantly cross-posted on a number of usenet newsgroups, and in some cases to unsolicited e-mail. Some have gone to considerable effort to put together packages of material, upload software to me, and dig out key bits of documentation.

If you think that civility and a sense of community is dead in the modern world, try looking up one of the original computer hobbyists from the late 1970's. All we had back then was each other. We learned to share.

A partial list of contributors follows. There are others but I don't have permission to list them here.

Dave Brockman aka "Big Dave"

I don't think I would have gotten this project under way without Dave's help. He's provided so much, including:

• the full HDOS 1.6 distribution software set;
• a binary image of the HDOS ROM (2K at 030.000A);
• H-19 escape sequences;
• I/O addresses;

...and a lot of early encouragement. Even the nifty picture of the H8 that graces the top-right corner of the home page.

Dave, I thank you, sir!

Larry Bledsoe

Larry dug through his stash of old H8 documentation and found some good information on H-17 disk rotation tuning — a great source for working out a number of timing issues — and some of the PAM8 material that I've been desperate to get. Thank you, Larry!

David Wallace

Jeeze, three Daves on the same project! And this Dave, believe it or not, is also working on an H8 emulator (http://home.attbi.com/~davidwallace2000/)! Only his runs on Windows/NT.

Dave and I have entered into a very helpful dialog on implementation issues, which is helping me sort through all the problems and potential problems — many of which he's already run into. Dave, I'm thoroughly enjoying the correspondence.

Dave also sent me the H8 front panel photograph I'd been looking for. That was a source of proportion and color information for the GUI. And he sent me the three-disk distribution of HDOS 2.0. Dave, I can't thank you enough.

Steve Novosad

Steve lent me rare and precious HDOS source code listings so that I could key in the PAM/8 ROM code, research I/O port definitions and usage, and get the H-17 disks working right. The PAM/8 listing was still in the original plastic shrink-wrap. Steve, thank you!

Charles Horn

Charles fought a reluctant disk drive in an H89 (he informs me that WD40 can fix anything!) to make me a disk with the makings of a PIE text editor, and threw in a copy of Video Scribe while he was there. Thank you, Charles!

Thomas Crosley, Walt Bilofsky, and Dean K. Gibson

These gentlemen graciously allowed me to distribute their software, the PIE text editor and the enhanced SY: device driver, on this site. Thank you for your continued support for the remains of the Heath computing comunity!

Andy Becker (e-mail)

Andy spent hours poring over the emu8080.c module and lobbying for specific performance improvements. Before: his machine was so slow that HDOS wouldn't boot reliably. After: his machine running in Turbo mode is now exceeding the speed of a real H8. He also provided benchmark tests, analysis, and dug up the Creative Computing Basic benchmark. Andy, I thank you.

Neal Granroth

Neal did extensive testing of the later versions of the emulator, pointing out a number of inconsistencies with the H-19 emulation in particular, and even providing test code to illustrate his points. Many thanks, Neal.

Stanley Webb

Stanley tested the 68K version on his older Performa 575 system, helping to lower the minimum system requirements to run the emulator. He also helped me find a nasty problem under OS 8.1 that I could not recreate here. Thanks much, Stanley.

Bob Meyers

Bob provided the PAM/GO ROM image from his still-running H8. Thanks, Bob.

go to top