ALLSTOP(OPCSDEFS)       Optical Printer Control System    ALLSTOP(OPCSDEFS)

    NAME
        allstop - define the ALLSTOP key

    USAGE
        allstop [port] [mask] [test] [0]    # (all values in hex!)

    EXAMPLES
        allstop 0060 7f 46 0                # typical for SCROLL LOCK key

    DESCRIPTION
        This command defines the allstop key for the software. The ALLSTOP
        button can be any key, or for that matter any bit on any port on the
        IBM PC, but keyboard's (`) key is recommended.

        All parameter values are in hexadecimal.

            [port] is the port number to read in the range 0000-03ff.
	    Use 0060 for the keyboard.

            [mask] is applied to the value received from the port 
            whenever the software is checking for an allstop condition.
            This is applied before comparing to [test].

            [test] is compared to the value read from the port after
            [mask] is applied. If the result is the same as [test], an allstop 
            condition exists.

            [0] is always zero.

        Under normal conditions, [port] is 0060 (the keyboard port), [mask]
        is usually '7f' (meaning mask off the high bit) and [test] is normally
        '29', which is the (`) key's keyboard scancode.

        The software essentially uses the following C code to read the port:

            if ( ( inp(port) & mask ) == test )
            { 
                /* An allstop condition exists  */
            }

    BUGS
        None.

    SEE ALSO
        DEENERGIZE(OPCSDEFS)  - define port/bit to deenergize motors
        ALLSTOP(OPDSDEFS)     - define port/bit to detect the allstop key
        BUCKLE(OPCSDEFS)      - define port/bit to detect film buckles
        VIEWER(OPCSDEFS)      - define port/bit to detect viewer open
        TRIPSWITCH(OPCSDEFS)  - define port/bit to detect trip switches
        SETBIT(OPCSDEFS)      - set bit(s) on a port
        CLRBIT(OPCSDEFS)      - clear bit(s) on a port
        XORBIT(OPCSDEFS)      - invert bit(s) on a port

    ORIGIN
        Gregory Ercolano, Los Feliz California 09/11/90