Hi, I lost my 84's IO link cable a month or so ago and have been looking for an alternative since.  I haven't been able to get a replacement.
Just today, I found the IO cable that came with my 9750.  I tried it with the TI calcs (math class ftw) but it didn't work.

So, I was wondering if there was a difference between ti's link cables and casio's link cables.  The plugs look just the same, but the TI calc always show "Error in XMit" as if nothing was plugged in.

TIA

Clarifying edit: I was meaning calc-calc linking

and let us not forget you need the driver from the TI cable to work with the Casio one too

It might be a simple wiring issue. Not sure, but I think that one might switch around the wires at the ends, so one's transmit is the other's receive, while the other is straight across, so there's a little more software interaction. Just a guess, but it seems likely to me.

That's quite possible.  An easy way to test it (if you have two 83+-series calcs) would be to use Calcsys's link console and see if all the bits come out flipped (e.g., if one calculator sends 55, the other receives AA.)  If the ground is swapped with one of the data lines, though, you won't be able to send anything at all.

Well, I only have one calc and since I don't have a link cable I can't really send CalcSys to another's calc...
Random idea that just might work: would it be possible for an ASM program or hook to intercept the link port commands and switch them?

Wait wait, if you have no other calc, how are you testing linking?

Well, I guess if you have Calcsys on your own calc, you could connect it to somebody else's calc and then have them attempt to send a variable.  The first thing you see should be (if I remember correctly) 73 68 00 00 - if the data lines are swapped, that would come out as 8C 97 FF FF.

You could, if you wanted to, write assembly programs to send and receive variables over a "twisted" cable (if that is, in fact, what it is.)  It wouldn't even be terribly difficult.  Getting the system I/O functions to work correctly, though, couldn't be done without modifying the OS.

I thought I/O is a universal cable? So it wouldn't be any different? Or maybe it's modified.

IO is usually expressed in single pins, on dev boards. there's no communication standard, it's just a bit mapped to in your memory. Arduino I/O pins work exactly the same way.