RC(4) BSD Programmer's Manual RC(4)NAMErc - SDL Communications RISCom/8 8-port serial multiplexor
SYNOPSIS
rc0 at isa? port 0x220 flags 0x0
DESCRIPTION
The RISCom/8 is an eight port EIA RS-232C (CCITT V.28) communications
multiplexor. It uses a block of 16 I/O ports selectable by on-board
switches. The block must be aligned on a 16 port boundary. The jumper-
selectable hardware interrupt level is detected during autoconfiguration
or alternatively can be specified in the system configuration file (in
this case no check is performed).
Each port may be independently set to any speed between 50 and 76800 bits
per second. On the original versions of the card, the 57600 speed is not
exact (it is slow by about 3%). SDL ships an alternate version of the
card which does provide correct clocking for 57600 baud. The newer ver-
sion of the card may be identified by examining the speed printed on the
oscillator on the card, the new crystal runs at 18.432 MHz. A flags
field of 0x1 in the kernel configuration file indicates the newer oscil-
lator frequency should be used. The kernel probe for the card will iden-
tify the card with the added tag: ``18.432 MHz crystal'' if the flags=0x1
was specified in the kernel config.
The failure mode for an incorrect setting of the flags field will be a
baud rate mismatch. There will be no other errors besides the incorrect
speed settings (which will only be detectable by connecting a device with
a specific baud rate setting). Many speed matching modems will continue
to work even with the mismatched rate, so they are not a good test of the
configuration.
The chip on the RISCom/8 may not be able to run all ports at the highest
rates simultaneously. The aggregate capacity is about 460800 bits per
second.
An open on the rc driver will block until carrier is present, unless
O_NONBLOCK or CLOCAL is set.
Multiple RISCom/8 boards may be present in the system at one time. The
least significant three bits of the minor device number select the line
within a card, and the next three bits select the card number.
DIAGNOSTICS
rc%d: illegal base address %x
Invalid port specification in kernel config file.
rc%d: illegal IRQ %d
Invalid irq specification in kernel config file.
SEE ALSOtty(4)HISTORY
The rc driver first appeared in BSD/OS.
BSDI BSD/OS January 30, 1995 1