NAME

     nmdm — nullmodem terminal driver

SYNOPSIS

     To compile this driver into the kernel, place the following line in your kernel
     configuration file:

           device nmdm

     Alternatively, to load the driver as a module at boot time, place the following line in
     loader.conf(5):

           nmdm_load="YES"

DESCRIPTION

     The nmdm driver provides two tty(4) devices connected by a virtual “null modem” cable.

     If either of the two tty devices have the CDSR_OFLOW bit (“stty dsrflow”) set in their line
     discipline, the nmdm device will emulate the speed configured in the termios(4) settings.
     The speed emulation works independently in the two directions, controlled by the slower
     end's termios settings (c_ispeed, c_ospeed, CS5 ... CS8, CSTOPB and PARENB).

FILES

     /dev/nmdmN[AB]  nullmodem device nodes.  Where the A node has a matching B node.

     The nmdm driver implements “on-demand device creation” so simply accessing a given instance
     in /dev will create it.

DIAGNOSTICS

     None.

SEE ALSO

     stty(1), termios(4), tty(4)

HISTORY

     The nmdm driver first appeared in FreeBSD 4.4.