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

NAME
     dcm - HP 98642A communications multiplexer

SYNOPSIS
     device dcm0 at 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]

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)

HISTORY
     The dcm driver currently under development.

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

OpenBSD 2.8                     March 27, 1991                               1
