Re: Dual port serial card?

[gtolar@ghgcorp.com (Glynne Tolar)]

In article <50pljr$rpg@flood.weeg.uiowa.edu>, snelson@news.uiowa.edu (Steven Nelson) wrote:
> (Scott Barker):
>> Has anyone ever heard of a dual-port serial card? I've got an apple // card
>> which claims to be one. I've got no docs, though. Any ideas how it might
> work?
>> 

Well, there have been 1 or 2 in the past.  The "Business Card" comes to
mind.  I think that is it name.  I think Street Electronics made it?
It and others used phantom slotting.  This made the parts of the card look
like they were in another slot.  There were usually DIP switches to define
what slots each part took.  You could not use these slots and these cards
were not compatable with the GS>  I think Promethious(sp?) made one too.

>What card?  The Apple IIe Workstation networking card has two serial ports.
>But I don't think that is what you are asking about.

I don't think so either.  But the card has posibilities.

>I've never seen one, but one could be done.  Most 6850 and 6551 based
>serial cards used only 4 addresses in the Cn8x space (6850 used 2, 6551
>used 4).  Since 16 addresses are available in that space, a quad-port
>serial card would not have to be too exotic.  Each port would be controlled
>by a different set of addresses.  If phantom slots were implemented, even
>more could be controlled.  

If you used some of the space that a card's ROM uses you could put even
more then 4 ports.  Or use the same address the 6551 does but another
address to "bank switch" which port you want to use.  I would think a better
card would be one with a microcontroller that could catch incomming data
or offload outgoing data to take the load off the CPU and allow it to process
other requests.  Like reading the hard drive (DMA stuff would get in the way
of an IRQ).  But with a uC you could have plenty of time to play catch up. 

>A multi-port serial card would be nice for a multi-line BBS system.  I
>don't know if any multi-line BBS systems were ever released for the AppleII.

Maybe if TCP/IP for GNO/ME ever comes out the demand for such a card
of the type I just described would be justify its creation.

>I do have an SSM SIO card that has two serial ports, one DCE and one DTE.
>Only one serial chip, and only one port was active at a time.  Preceeded
>the Apple SSC card that used the terminal block to switch between DCE
>and DTE configs for just the single port connector.  Are you describing
>something like this?

I suspect that it only has one port and each "port" was just a rewiring of the 
other.