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Question concerning Asynchronous comm card

JollyRogers

Member
Joined
Sep 18, 2008
Messages
19
I have an asynchronous communication card in my XT, and there's a ribbon cable running from it to a female DB25 port on a plate at another expansion slot. My question is, does the female DB25 port act as a serial port or parallel port?
 
Hmm..a female DB25 (with holes that the pins go into) in normally associated with a parallel port on old IBMs. However the asynchronous communication cards I'm familiar with all have male DB25s and they are serial?

Tez
 
It must be an aftermarket card with the auxiliary DB25, not an original IBM, and it's definitely a parallel port. Other than the original PC serial card I don't recall any ISA-bus communications cards using anything other than a DB9 for serial.
 
You must be pretty young then, because, at one time, parallel ports were DB25F and serial ports were DB25M. The only DB9s were video.

Exactly, the AST adapters had DB-25s for serial connections. The AT is what actually *started* to bring in the DB-9M for serial. Even then, I still have quite a few DB-25M connections on a 10-pin header to use the ¨old-style¨ connections.
 
As a matter of fact, many of the multi-IO cards had one of each (9 and 25 pin).

Except for a few early sort-of-compatibles, in the PC world the parallel port has always been a 25-pin female, and the serial port(s) either 9 or 25 pin male. BTW, the gender refers to the pins (the shell is actually the opposite gender).

A female DB-25 on an async card is definitely an oddity; either there's also a parallel port on the card, or someone has made a custom cable or used a printer cable instead of the serial.

If by female you are indeed referring to holes for the connecting pins then it's definitely non-standard and I'd check it out further before connecting something and possibly causing damage.

m
 
I can take a photo if it helps, but basically the card has a male DB25 on it, then a small ribbon cable running to a DB25 female. I'm considering just hooking a printer up and seeing what happens. Worst case scenario, I have another Asynchronous communication card.
 
Well, if anything does get damaged in your worst case scenario it's actually more likely to be the printer.

Sounds like you may have a printer cable on the second port instead of the DB-25M serial. A picture would be good, especially if we can see the main chip numbers; if there are just two UARTs then they're both serial. Maybe someone wanted to plug in a male serial cable and didn't want to use an adapter.

If you've got a meter you could measure the voltages on the external DB25 and compare them to the one on the card.

m
 
It's easier than that usually...

99% of the serial ports I've seen over the years have had a 9 pin ribbon cable connecting it. Does the one you have on the computer have only 9 pins on the ribbon cable? If so, it's serial.

RJ
 
It's easier than that usually...

99% of the serial ports I've seen over the years have had a 9 pin ribbon cable connecting it. Does the one you have on the computer have only 9 pins on the ribbon cable? If so, it's serial.

RJ

All the ones I've seen have 10 pin headers regardless of the DB shell pin count. A parallel port header will have 26 (2 x 13) pins on the header and the game port, a 16 pin header.
 
To really confuse things, Radio Shack manufactured serial cards with 25 pin female connectors for quite a while too. I had one here in my 1200 hd for years.
 
To really confuse things, Radio Shack manufactured serial cards with 25 pin female connectors for quite a while too. I had one here in my 1200 hd for years.

Perhaps to maintain 'plug compatibility' with earlier computers (Kaypro, Morrow, TRS-80, etc) which used female 25-pin DIN jacks for serial ports?

--T
 
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What's the 'A' mean?

I've got some TM100s, FH 48TPI/DD as used in PCs, if that'll do ya; might need alignment though...

m

I have NO idea what the 'A' stands for. As long as it'll do 360K, I'm sure the 1200HD won't mind a bit.

Alignment? No problem, I'm just going through a stack of Texas Peripheral SSDD drives (10-5355-001) aligning them
 
So, I was inside my XT today and found out that the serial card in question was in fact a SixPakPlus! (Turns out my motherboard is the 64-256KB board, not the 256-640KB board I thought it was) The DB-25 Female port is indeed an LPT port. Mystery solved, and would have been solved sooner if only I knew more about machines of this age. Live and learn I suppose.
 
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