NAME    [Toc]    [Back]

     dcm - HP 98642A serial communications multiplexer

SYNOPSIS    [Toc]    [Back]

     dcm* at dio? scode ? flags 0xe

DESCRIPTION    [Toc]    [Back]

     The 98642A is a four port EIA RS-232C (CCITT V.28)  communications multiplexer.
   The  98642A has three direct-connect ports and one
port with full
     modem control.

     Input and output for each line may be set to one of the following baud
     rates:  50, 75, 110, 134.5, 150, 300, 600, 1200, 1800, 2400,
4800, 9600,
     19200, 38400.

     Flags is usually specified as 0xe since 3  of  the  4  ports
(1-3) do not
     support  modem  control  and should be treated as hard-wired
with carrier
     always present.  If port 0 does not have the need for  modem
control then
     flags can be specified as `0xf'.

     Each  port  on the 98642A has a 128 byte input silo and a 16
byte output
     silo.  Interrupts happen on a per character basis unless the
interrupt
     rate  for the card reaches 70 interrupts per second at which
time the
     driver changes  to  a  16.7ms  (60  interrupts  per  second)
polling scheme until
 the interrupt rate drops.

FILES    [Toc]    [Back]

     /dev/tty0[0-9a-f]
     /dev/cua0[0-9a-f]

DIAGNOSTICS    [Toc]    [Back]

     dcm%d  port%d:  silo overflow  Input Silo has overflowed and
incoming data
     has been lost.

     dcm%d port%d: uart overflow  The 3 character buffer  in  the
UART has overflowed.

SEE ALSO    [Toc]    [Back]

     apci(4), dca(4), dio(4), intro(4), tty(4)

BUGS    [Toc]    [Back]

     Total throughput per card, all ports together, is limited to
76800 bits
     per second continuous input rate.

OpenBSD      3.6                           June      9,      1993