fc(4)fc(4)Namefc - VAXstation serial line interface
device fc0 at ibus? flags 0x0f vector fcxrint
This serial line interface is similar to the DZQ11 four-line communica‐
tions multiplexer. An interface provides four communication ports with
partial modem control on port 2, adequate for dialup use. Only port 2
supports modem control (dialup access), all other ports must be oper‐
ated as local lines. Each line attached to the serial line controller
behaves as described in and may be set to run at any of 16 speeds. For
the encoding, see However, configuration requirements dictate fixed
speed operation of ports connected to the console terminal and graphics
The ports are configured as follows:
0 Graphics device keyboard at 9600 BPS
1 Mouse or tablet at 4800 BPS
2 Communications (with modem control)/local terminal
3 Serial printer port at 9600 BPS
A diagnostic console terminal may be connected to port 3. When the
diagnostic console is in use, the processor may be halted by pressing
the BREAK key. The selection of which port to use for the console is
made during the processor's power on sequence and cannot be changed
after power on. If the Low End Graphics Subsystem (LEGSS) console is
present, it will be used; otherwise the device connected to port 3 will
be the console.
For the device, the flags should always be specified as ``flags 0x0f''
(all 4 lines hardwired). The state of port 2 may be established by
specifying either modem or nomodem as part of the file entry for tty02;
see The default state of port 2 may be controlled by flags bit 2. Set
``flags 0x0f'' for a hardwired line, ``flags 0x0b'' for dialup opera‐
tion (wait for carrier).
The driver operates in interrupt-per-character mode (all pending char‐
acters are flushed from the silo on each interrupt). Silo alarm mode
is used by the DZQ11 driver at times of high input character traffic.
This mode is not used by the driver, due to the need to track mouse or
tablet position changes in real time.
Speed must be set to 9600 BPS on the console port, 9600 BPS on the key‐
board port, and 4800 BPS on the mouse port. The fc driver enforces
this restriction; that is, changing speeds with the stty command may
not always work on these ports.
fc0: input silo overflow
The 64-character input silo overflowed before it could be serviced.
This can happen if a hard error occurs when the CPU is running with
elevated priority, as the system will then print a message on the con‐
sole with interrupts disabled.
/dev/console console terminal or graphics device
/dev/tty00 not used
/dev/tty01 local terminal - multiuser configuration only
/dev/tty02 dialup or local terminal
/dev/tty03 printer port or local terminal
/dev/mouse mouse or tablet - workstation configuration only
/dev/fcscreen console message window for workstations
See Alsoconsole(4), devio(4), tty(4), ttys(5), MAKEDEV(8)