dcm(4)
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DCM(4) NetBSD/hp300 Kernel Interfaces Manual DCM(4)
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 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 ALSO
dio(4), tty(4)
BUGS
Total throughput per card, all ports together, is limited to 76800 bits
per second continuous input rate.
NetBSD 5.2 June 9, 1993 NetBSD 5.2
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