NAME
    AllocPotBits -- Allocate bits in the potgo register.

SYNOPSIS
    allocated = AllocPotBits(bits)
    D0                       D0

    UWORD AllocPotBits( UWORD );

FUNCTION
    The AllocPotBits routine allocates bits in the hardware potgo
    register that the application wishes to manipulate via
    WritePotgo.  The request may be for more than one bit.  A
    user trying to allocate bits may find that they are
    unavailable because they are already allocated, or because
    the start bit itself (bit 0) has been allocated, or if
    requesting the start bit, because input bits have been
    allocated.  A user can block itself from allocation: i.e.
    it should FreePotgoBits the bits it has and re-AllocPotBits if
    it is trying to change an allocation involving the start bit.

INPUTS
    bits - a description of the hardware bits that the application
            wishes to manipulate, loosely based on the register
            description itself:
        START (bit 0) - set if you wish to use start (i.e. start
                the proportional controller counters) with the
                input ports you allocate (below).  You must
                allocate all the DATxx ports you want to apply
                START to in this same call, with the OUTxx bit
                clear.
        DATLX (bit 8) - set if you wish to use the port associated
                with the left (0) controller, pin 5.
        OUTLX (bit 9) - set if you promise to use the LX port in
                output mode only.  The port is not set to output
                for you at this time -- this bit set indicates
                that you don't mind if STARTs are initiated at any
                time by others, since ports that are enabled for
                output are unaffected by START.
        DATLY (bit 10) - as DATLX but for the left (0) controller,
                pin 9.
        OUTLY (bit 11) - as OUTLX but for LY.
        DATRX (bit 12) - the right (1) controller, pin 5.
        OUTRX (bit 13) - OUT for RX.
        DATRY (bit 14) - the right (1) controller, pin 9.
        OUTRY (bit 15) - OUT for RY.

RESULTS
    allocated - the START and DATxx bits of those requested that
            were granted.  The OUTxx bits are don't cares.