DCM

Section: Devices and Network Interfaces (4)
Updated: hp300
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BSD mandoc
 

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 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

tty(4)  

HISTORY

The driver Ud  

BUGS

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


 

Index

NAME
SYNOPSIS
DESCRIPTION
FILES
DIAGNOSTICS
SEE ALSO
HISTORY
BUGS

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Time: 06:48:21 GMT, May 19, 2025