DCM man page on 4.4BSD

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DCM(4)		      BSD/hp300 Kernel Interfaces Manual		DCM(4)

     dcm — HP 98642A communications multiplexer

     device dcm0 at scode? flags 0xe

     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,

     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.


     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‐


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

BSD				 June 9, 1993				   BSD

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