DCM(4) BSD/hp300 Kernel Interfaces Manual DCM(4)NAMEdcm — 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
until 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 ALSOtty(4)BUGS
Total throughput per card, all ports together, is limited to 76800 bits
per second continuous input rate.
BSD June 9, 1993 BSD