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NEC APC and Serial Communications

glitch

glitch

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I've finally gotten a copy of Kermit-86 up and running on my NEC APC under CP/M-86 -- now the trouble is I'm not sure that it works. Loopback tests fail. The APC uses Centronics 36-pin connectors for both parallel and serial connections, so I thought perhaps it was a weird pinout that I was goofing up. I got out my 8251 "test socket" (a DIP socket with pins 3 and 19 bent up and soldered together -- RxD to TxD directly) and still no loopback. I've changed the 8251A with a known good device, too. I haven't gone further in testing as the board is hard to probe while in the slot, and I don't have an extender for the APC. Any ideas?
 
Well, are you sure you're accessing the 8251? I mean do the registers read back okay?

...and I assume it's an 8251A; the 8251 was a real nightmare of a chip.

Are you running DOS or CP/M-86?
 
I'm not sure yet...the APC doesn't have a monitor program, so I'll have to write some 8086 ASM to push/pull data from the registers. Problem is, I don't know 8086 ASM...yet!

Yes, it's an 8251A. I have several S-100 boards that use the 8251A so I've got some known good devices on hand.

I'm running under CP/M-86 at the moment, though I do have MS-DOS 2.11. I'm more interested in the CP/M side of the APC, but do plan on implementing at least XModem for MS-DOS on the APC at some point.
 
If it were my system, I'd poke around abit with SID86, writing little test programs and seeing what happens. Right now, apparently you don't even know if you've got the I/O address right (it definitely isn't the same as on a regular PC). Getting PC98 documentation not in Japanese is a real chore.
 
Where can I find SID-86? Google has yielded manuals, but no binaries.

I looked through the Kermit-86 include for the APC and the APC's 8086 ASM manual...looks like there are some big port differences. I'll probe around with the two sets of ports and see if either actually talks to the 8251A.
 
I've got SID-86--it's part of the DR Assembler Package. Is it on Gaby's site?

But yeah, the NEC APC/PC98 platform is very very different from the IBM PC. DOS even uses a different sector size (1024 bytes).

The APC is closest to the NEC PC9801--it came out of a different division, but shares a lot of similarities.

Maybe this will give you a hint
 
Thanks Steve! I now have SID-86 working on my CompuPro and the APC! Used it to test my N8VEM/S100Computers.com Serial IO board tonight!

Chuck, that does indeed help...it seems to confirm the ASM in the Kermit source, leading me to believe there might be a problem with my APC's serial controller. I'm going to manually push stuff into its 8251A's control port and see if I can at least get status changes.

To prepare for the work in getting Kermit-86 running on a maybe not entirely functional machine, I think I'm going to first work on writing a Kermit I/O driver for the N8VEM Serial IO board, since that's a known working device. Plus, as far as I can tell, no one has done that yet!
 
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