DCM(4)                OpenBSD Programmer's Manual (HP300)               DCM(4)

NAME
     dcm - HP 98642A serial communications multiplexer

SYNOPSIS
     dcm* at dio? scode ? flags 0xe

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

     Input and output for each line may set to one of 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 un-
     til the interrupt rate drops.

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

DIAGNOSTICS
     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 over-
     flowed.

SEE ALSO
     tty(4)

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

OpenBSD 3.0                      June 9, 1993                                1
