505 board converting to serial output

[nama]

Ok, some good news. After a full weekend of working on this, at midnight on Sunday I was finally able to fix all the RAM issues. I now have 24k fully working.

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[nama]

...after much troubleshooting I realised that the RAM issues were caused by a badly designed (or redesigned) backplane. Can't remember who I got this from but the solder pads are covered with a layer mask so soldering was a challenge. I knew that at the time, but I didn't realise that it would cause so many issues. See the photo showing the solder side with no pads to solder too, and the non solder side which actually have loverly solder pads. Frustrating and basically took up half a day of troubleshooting.
I am considering removing all the pin headers, flipping the backplane board and soldering everything back together, but upside down, so I can utilise the good solder pads. What do you think?

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[nama]

I'm entering the next stage of the build, which means converting it from a serial machine into a video system with disk access.
I am still gathering the parts to build one of Dave's Unified retro keyboards, so until I do that I wont have any way to 'input' if I swap the Serial ROM (SYN600 with 65V monitor for 540/542 @ relative page 2) that Danny sent me with a standard SYN600 ROM. I have built another of Klyball D-13 data splitter, and have set the timing on that.

So with the Danny's serial ROM in place, the D-13 installed, and a known working (in OSI systems) flash floppy gotek installed, and pressing 'D' on terminal software at the H/D/M menu prompt I get absolutely no activity at all on the Gotek.

So my question is, with the ROM configured with 65V should it still work for disk access?

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[bxdanny]

Are you seeing the H/D/M? on both the 540 video screen and the serial terminal? You should be. If you type M (or anything else except H or D), do you enter the serial monitor program (which is 65A), with the ability to load and dump memory contents? If so, then the floppy boot code should certainly be executed when you press D (uppercase), since it is in the same ROM page as the code that outputs the H/D/M? in the first place. I just took a look to verify that the boot code is in place in the ROM image I made for you, and it is, and doesn't appear damaged. So perhaps there is a problem with [Edit:] the disk interface on the 505 board.

[nama]

Thanks for the reply Danny.
Yes, basically serial is working well.
Today I spent quite a few hours going over the board and undoing the 8" mods that had been done. Not sure why I didn't check this before, I guess I just assumed it was setup for 5.25" floppies. A lot of wires installed to temporarily jumper the cut traces that were done for the 8" mod. Also replaced a 4.7k resistor for an 18k one (another 8" floppy mod), and re-did all the timing as per the SAMs manual.
I can now run the TestDisk program (https://www.pdp8online.com/osi/osi-floppy-test.shtml) and finally the gotek drive works and seems to pass all read/write tests on all tracks (with very occasional errors. Maybe one error in every 4 complete passes)...strangely enough restarting the machine back to the H/D/M menu and pressing 'D' still does absolutely nothing! Not a pip from the drive...nada!

Phil

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[bxdanny]

Very odd that the test program (loaded via serial port) works, but booting from disk with "D" doesn't. I think I did verify that the ROM image I sent you can boot disks.

Maybe try going directly to the bootstrap routine rather than selecting "D"? I can't really see why it would make a difference. Maybe you are receiving an interrupt when trying to boot the disk, and the CPU is getting lost? IRQ is disabled when the 6502 is reset, but NMI can't be blocked. You could try this from the Monitor:

L012C 04 FC 0133 4CA0FF 2000FF 4C0022 R
G

That puts JMP $FFA0 (the reset address) at the NMI vector of $0130, and then calls the bootstrap routine at $FF00. If you were getting one NMI, then you should see H/D/M? repeated when you press "D". Or you could just try lifting up the 6502's NMI pin (pin 6), and then doing a normal <reset>D when you power back on.

[nama]

Hi Danny,
I tried your code.
The machine just seems to hang after the final 'G'...nothing happens.
I also tried lifting the NMI pin on the 6502 (pin 6) and reseting and then 'D', but that doesn't seem to change the behaviour of the machine at all.

[bxdanny]

OK, well at least I tried, and you tried.

The last thing I can think of is to try a copy of the boot code in RAM. The attached file, which could be sent to the OSI through the serial port, does that. It is slightly modified to set the PA6 (drive B select) line as an output right from the start, but otherwise is just a relocated copy of the ROM bootstrap code. I don't really think it's likely to work at this point, but it just might be worth a try.

Edit: I presume you've tried it with only one drive connected, so the business about the B drive select line shouldn't matter. In fact, it might even make things worse if both drives were connected. So really, this is just in case the boot code in your ROM is corrupted somehow.

[nama]

Thanks again.
Yes, just the one drive

I tried the code you sent, and again it just hangs after the 'G' with no activity on the drive at all.
Curious

[nama]

I wonder if the drive is in a state that the boot code sees as 'not ready', but the test disk program ignores?

EDIT: Spent some time looking into the above and trying various different config settings. In the end I plugged the Gotek back into my Superboard, and it didn't boot, so I just reset all the settings back to what they previously were and the superboard booted fine again...so I'm assuming the Gotek is basically fine.

I also tried a floppy dump program (Disktool) and that seemed to work fine, and I was seemingly able to dump the contents of a floppy via XModem.

EDIT #2: I'm curious if 65A is expecting 8" disks, or is it format agnostic?