Reading / Writing from the Paper Tape Reader Using Boot Loader from IMSAI Manual

[ronaldlw]

For some insane reason I decided to try to get the tape bootloader code to work on my IMSAI but am running into issues at the very start. The Keyed in code is using ports 03 and 02, are these correct for this tape reader?

[udo-munk]

Ports 2/3 are SIO 1 channel B, which is used for the VIO keyboard. The paper tape would be connected to SIO 2 channel A, ports 34/35.

[ronaldlw]

Awesome, thanks @udo-munk , i'll give that a try. I was trying to follow your video to write and read from the paper tape with xybasic but it's not working on the imsai, is there some extra configuration that is hidden behind the curtains that I need?
https://youtu.be/512cTkNgH3A?si=u4GxCeRsiTFd3H-E

[ronaldlw]

not having much luck, are those numbers decimal or hex? tried both but it seems to be reading in garbage. also is 35 the out port and 34 the data port?

Is this documented somewhere? (the ports)

[udo-munk]

The port numbers are in decimal and 34 is data and 35 is status.
It is kinda documented in the sources. This module maps the port number to the devices and can be used as reference:

https://github.com/udo-munk/z80pack/blob/master/imsaisim/srcsim/simio.c

[ronaldlw]

I made some good progress, those ports are not hex. and my issue is the "second level bootstrap" tape needs to have a "direct core image" i.e. the actual binary data instead of text hex file.

So I guess I have to figure out how to dump the actual memory image of the file to disk somehow then write that to a tape.

Any hints on that would be appreciated!

I'll keep poking in the meantime.

[udo-munk]

I would enter the bootstrap sources, assemble this to a binary file (z80pack z80asm -fb ...), and then fiddle this all together into a tape file with UNIX tools.

[ronaldlw]

Ok, I managed to get this done by copying the source into cp/m on the imsai, running asm on it, punching the hex file to tape, downloading it to my computer, editing it in notepad++ to remove the misc junk, copied it to a linux host and used xxd -r -p on it to convert it to binary.. whew.. :)

So the process called out in the manual is to punch a tape with that binary at the beginning and the final loader program following that.

I was able to do that by loading in the binary file to the tape then doing a pip ptp:=(final loader program hex file)

Now... the issue seems to be that the tape doesn't support xon xoff to stop the tape. the 2ndary boot loader (and the final one) both rely on that to stop and start the tape in multiple places.

Is that a setting I need to change or is it just not implemented?

So what happens is the keyed in bootloader loads the binary info off the tape and just puts it right after it's code so once it reads in the binary data it falls through to the loaded program. Then the first thing that program does is stop the tape:

[udo-munk]

XON/XOFF is not implemented, this won't work. Try with commented out waiting for XON, should work then.

[ronaldlw]

Thanks @udo-munk ! what are the odds of implementing xon/xoff? Where exactly is the code that implements the tape, I poked around in the iodevices dir on github, but didn't find it.

[udo-munk]

The tape device is implemented in the WEB GUI. The upper end connecting to the GUI devices or others is implemented in HAL here:
https://github.com/udo-munk/z80pack/blob/master/iodevices/imsai-hal.c
And the SIO's self at lower end here:
https://github.com/udo-munk/z80pack/blob/master/iodevices/imsai-sio2.c

I think XON/XOFF needs to be implemented in the tape device self, I don't know how difficult that would be.