NAME
dcm —
HP98642A serial communications
multiplexer
SYNOPSIS
dcm* at dio? scode ? flags 0xe
DESCRIPTION
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 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 overflowed.
SEE ALSO
hp300/dio(4),
tty(4)
BUGS
Total throughput per card, all ports together, is limited to 76800 bits per
second continuous input rate.