serial ports on the '286

[pri=-10 Stuart Lynne]

In article <4690 at b-tech.UUCP> zeeff at b-tech.UUCP (Jon Zeeff) writes:
>In article <531 at micropen> dave at micropen (David F. Carlson) writes:
>>
>About the serial port problems on the '286.
>
>I think serious thought should be given to supporting the NS16550AN.  
>This is a plug in replacement for the existing uart that gives you a 
>16 byte fifo.  At least the problem would go from "there is nothing 
>that can be done" to "you need to buy a new chip".  I don't know what 
>the cost is though.  
>

This chip makes a very large difference to any 286 or 386 based system,
provided you have a driver which can utilize it.

I'm just finishing a multi-port card driver for a customer which supports this
chip (just have to do the install disks). 

Because it is a commercial product I can't distribute the source but
is there any interest in low cost (~$50) version which will support the
standard IBM ports and some generic multiport cards?

This driver also supports the 8250, and 16450. A fair amount of work went
into making the driver as efficent as possible for these chips including an
assembler interrupt service loop.

Each serial port has three device's associated, with/without modem control
and with modem controls for getty. This allows for very simple use of a
modem for incoming and outgoing calls without having to turn the getty on
and off. Simply enable the getty on the getty device. The open does not
complete until carrier is detected. Opens on the other devices are blocked
if the getty device is fully open. If they succeed the getty device is
blocked until they are finished.

Full duplex CTS/RTS flow control is supported. It is enabled with the 
RTSFLOW/CTSFLOW termio bits if your system has them (late model SCO XENIX)
or via a bit in the minor device number.

You can configure up to thirty two port addresses, four interrupts, with a
maximum of sixteen ports per interrupt. The driver automatically determines
whether you are using an 8250, 16450, or 16550 device.

Currently the driver runs on Bell Tech 386, SCO Xenix 386, SCO Xenix 286, and
IBM Xenix 286. Microport 286 shouldn't be too hard.

The 16550 part is available but hard to get. Try Arrow(?) and
Hamiliton-Avnet. Cost should be under $30. With this chip in place you get a
16 byte FIFO for both incoming and outgoing data. This substantially reduces
the system overhead. One test we did showed that for supporting two outgoing
19.2 datastreams the system overhead was about the same as for a popular
smart card doing the same.


-- 
Stuart.Lynne at wimsey.bc.ca {ubc-cs,uunet}!van-bc!sl     Vancouver,BC,604-937-7532