HP 98642A serial communications multiplexer
dcm* at dio? flags 0xe
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
Input and output for each line may be set to one of the following baud rates:
50, 75, 110, 134.5, 150, 300, 600, 1200, 1800, 2400, 4800, 9600, 19200, 38400.
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
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
- dcm0 port0: silo overflow
- Input Silo has overflowed and incoming data has been lost.
- dcm0 port0: uart overflow
- The 3 character buffer in the UART has overflowed.
Total throughput per card, all ports together, is limited to 76800 bits per
second continuous input rate.