NYM(4)

NAME
nym - Nymos quad RS232 serial interface card driver

DESCRIPTION
The Nymos quad RS232 expansion card allows up to 4 RS232 serial lines to be attached to an Acorn R140 or R260 computer. Each line may be used for any device conforming to (a subset of) the RS232 interface standard, such as terminals, printers, plotters, etc. The standard BSD 4.3 ioctl and POSIX tcsetattr interfaces may be used to access and control each device independently (see tty(4)).

The hardware provides support for line speeds up to 38400 baud in each direction. However the current driver rejects attempts to use 38400 baud for either input or output, returning EINVAL; this restriction may be lifted in a future release of the operating system. In addition, certain combinations of input and output speed are not supported by the hardware, and are rejected with EINVAL. The illegal settings are any input baud rate from the set {50, 200, 38400} in conjunction with any output baud rate from the set {75, 150, 1800, 19200}.

Each physical serial port provides 4 signal connections and ground (see hardware documentation provided with the card). The signals are TxD (Transmitted Data), RxD (Received Data), RTS (Request To Send) and CTS (Clear To Send). As such, there is no provision for the DCD (Data Carrier Detect) or DTR (Data Terminal Ready) lines normally used to handle a modem. However the driver provides a measure of support for this by mapping the function of DTR (input to a modem) onto the RTS output; the RTS line is set high when the tty is opened by a process, and dropped when the tty is closed, or the line speed is set to 0. In addition it may be dropped and raised by a program using using the TIOCCDTR and TIOCSDTR ioctl(2) commands.

Normally the CTS input line must be strapped high to enable the transmitter, but this may be overriden with the TIOCLSET ioctl(2) command, by setting the LMDMBUF flag. Note that the driver does not input the normal meaning of the LMDMBUF flag, since there is no DCD input.

For simple local terminal use (i.e. not via a modem), it suffices to wire the RTS output to the CTS input, leaving the standard 3 wires (input, output and ground) to attach to the device.

SEE ALSO
tty(4),gettytab(5),ioctl(2)

ACKNOWLEDGEMENTS
The original driver was written by The Instruction Set Ltd; it has been modified by Acorn. Some of the information here was derived from the original manual page, also written by The Instruction Set Ltd.

NOTES
This manual page supercedes the original Instruction Set one supplied in paper form with the expansion card hardware.