Library /sys$common/syshlp/nclhelp.hlb loop, loopback_application, format  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    The optional Format argument is an octet (00-FF) which specifies
    the value of each byte in the test data part of each loop message.
    The default results in alternating 0 and 1 bits (55).

    loop [node node-id] loopback application name full-name, -
         format octet [,optional arguments...]

    loop [node node-id] loopback application address tower-set, -
         format octet [,optional arguments...]

    Example:

    loop loopback application name DEC:.SCH.LAMCHP, format FF