TENSION(OPCSDEFS)	Optical Printer Control System	  TENSION(OPCSDEFS)

    NAME
        tension - configure tension motor port for each channel

    USAGE
        tension [chan] [port] [mask] [invert] [softlatch]    # (values hex!)

    EXAMPLES
        tension a 03bc 01 00 0        # lpt1 output port bit #1
        tension a 0306 01 00 1        # RTMC16 logic connector bit #1
                                      # (note [softlatch] set to 1)

    DESCRIPTION
        Defines the port/bit combo that controls the film tension motors for when
	the specified [chan] changes direction.  Intended only for cam/pro/pro2
	(channels a/b/c) to maintain proper tension on the film.
	
	[chan] is the channel name of the motor to be affected.

	[port] is the hard port. 0000 disables tension motor control.

	[mask] is the bit on the port that manages the tension motor.

	[invert] if '0', running forward clears the [port] bit in [mask],
                 and running reverse sets it. If '1', the opposite occurs.

    CAVEATS
        o With [softlatch] set to 1, only ports 0x0000 - 0x07ff are allowed.
          Any ports above 0x07ff with [softlatch] enabled causes an error.

        o External programs changing port bits defined to OPCS with [softlatch]
          (e.g. the kuper logic I/O port) should be aware that OPCS is
          maintaining its own internal latch for that port, and that latch
          won't know about hardware changes made by external programs.
        
        o Due to these issues, it's best to avoid using hardware that has to
          be latched. It's usually bad hardware practice to make WRITE ONLY
          ports, since different programs cannot co-communicate with them,
          unless some common data area or driver is arranged.

    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