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As Tim says, the key is to have the H-8-5 serial interface card. Thomas: do you have this board on your system? The PAM monitor load/dump routines are specifically designed to work with this board. The later H-8-4 serial card is a wonderful board but is more useful in a disk-based setup.
The H-8-5 has two 8251 universal synchronous asynchronous receiver transmitter (USART) chips; one intended for interfacing to the console (typically an H9 terminal back in the early days) and one for loading software (typically a cassette drive back in the early days). I have successfully used Dave Runkle’s adapter to convert the second 8251 (cassette port) into an RS232 serial port which can be connected to a PC (see his writeup “Adding a RS232 Interface to the H8-5 Cassette Interface” at http://www.astrorat.com/heathkit/heathkith8computer.html). I then have been able to load the various tape images (in “H8T” format) using a PC to replace the cassette drive. There is a set of images at https://sebhc.github.io/sebhc/software/tapes/tape-images.zip. The very early H8 documentation can be helpful with this (“Software Reference Manual” 595-2048). I have a paper copy but am not sure if/where there’s a PDF of this.
Now I believe it is not necessary to actually build this adapter as the original H-8-5 was also designed to work with ASR teletype machines, which were popular among early computer hobbyists. Using the “port interchange” switch on the board I believe you can use the first USART to do double duty, functioning as both a console port and a serial interface port. This feature was intended to support paper tape punch/readers which were a common accessory in the ASR world. I haven’t worked out the details on this but it seems like putting the switch in “PORT INTCHG” mode will let you do this. See the H-8-5 manual at the link provided in Tim’s email, and specifically page 44.
Let us know if you are successful and/or if you need more help. It would be good to document how to use this feature with a modern PC setup and serial connection…
Davie Troendle and I have also resurrected some of the very early BASIC programs from HUG volumes I-V (which were published only in printed form). I haven’t posted this anywhere, mostly since I didn’t perceive too much interest, but both Tim and Thomas, and perhaps others may be interested since it lets you load and run software without relying on ancient cassette recorders and without needing an operational H17 disk system. If there’s interest I can provide more help/info here…
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On Jun 26, 2021, at 7:29 AM, Thomas Riesen <gast...@gmail.com> wrote:
@all: Thank you for your help!
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<Heathkit_H8_rt_01.jpg>
Just to clarify, it’s the (older, 1977) H-8-5 serial board that has the optical isolation. Heathkit clearly wasn’t thinking in terms of anything we’d call “high speed” today. In the instructions they recommend setting the board to 110 BAUD for Teletype; 300 BAUD for the “high speed” H36 (LA36 DecWriter II); and 600 BAUD for the H9 video terminal! I can’t remember but don’t think the H9 could even go past 4800? 😊
When the H19 and H-8-4 came out (1979) 9600 BAUD became standard for Heathkit (and the aftermarket soon was pushing that to 19.2K and higher).
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