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NAME

     nmdm - nullmodem terminal driver

SYNOPSIS

     device nmdm

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.