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DCM(4)                 NetBSD/hp300  Programmer's 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 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

     dio(4), tty(4)


BUGS

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

NetBSD 1.6.2                     June 9, 1993                                1