DCM(4) (hp300)

DCM(4) | Device Drivers Manual (hp300) | 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 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.

February 17, 2017 | NetBSD 11.0