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                23.1    SPECIFICATION  . . . . . . . . . . . . . . . . .  23-2
                23.1.1    CAMAC Commands . . . . . . . . . . . . . . . .  23-2
                23.2    CONSTRUCTION . . . . . . . . . . . . . . . . . .  23-3
                23.2.1    Single-width CAMAC Module  . . . . . . . . . .  23-3
                23.2.2    Front Panel with:  . . . . . . . . . . . . . .  23-3
                23.3    DRAWING PACKAGE NUMBER . . . . . . . . . . . . .  23-3
                23.4    RESPONSIBLE ENGINEER . . . . . . . . . . . . . .  23-3

                                      CHAPTER 23
                            MOVING MAGNET CONTROLLER (MMC)
        The MMC is a single-width CAMAC module designed to provide the digital
        control  for  48  stepping motors.  Its primary application is for the
        control of the magnet-moving stepping motors located in the SLC  arcs.
        The  module  drives all 48 motors quasi-simultaneously by multiplexing
        the control pulses.  It does this by keeping a register for each motor
        into  which  is read the number of steps required and the direction of
        rotation.  It looks at each register in turn and, if the value is  not
        zero,  it  sends  out a command to the stepping motor to move one step
        and decrements the register.   The  command,  which  is  sent  to  the
        Stepping  Motor  Driver (SMD) crate (described in a separate chapter),
        consists of 6 bits of address information, a bit to give the direction
        of rotation and a strobe.  The MMC also receives input from this crate
        in the form of two status bits which are dependant on the total  drive
        current  supplied by the crate power supply.  If this exceeds 7 A, the
        MMC goes into a wait state and does not issue any further commands for
        motor  movement  until  the  current  falls below this value.  Each of
        these bits is carried on a separate differential  pair  in  the  cable
        between the two units.
        The basic frequency is derived from a 10 MHz clock.  The motors run at
        100  Steps/Second.   However,  there  is  a hardware limitation to the
        number of motors that can be run at any one time.  f the  motor  power
        supply  exceeds  7 Amps then the motor mover algorithm will halt until
        such time as the current limitation is removed.
        It should be noted that no control of  speed  or  of  acceleration  or
        deceleration is provided in this module, nor does it keep track of the
        motor position.



        MOVING MAGNET CONTROLLER (MMC)                               Page 23-2


        23.1  SPECIFICATION


        23.1.1  CAMAC Commands

         Status
                F0 A(N)  Reads value of motor(N) where N < 17.  R1-R16 contains
                         number of steps remaining.  R16 = sign.
                         Value in 2's complement.
                F1 A(N)  Ditto for motors 17 to 32
                F2 A(N)  Ditto for motors 33 to 48
         Control
                F16 A(N) Writes a value to a memory location.  This is the
                         number of steps motor(N) should take where N < 17
                         Overwrites all previous values.  Starts motor.
                         Format is 2's complement, similar to Joerger module.
                F17 A(N) Ditto for motors 17 to 32
                F18 A(N) Ditto for motors 33 to 48
                F24 A(0) Pause. The result is to stop the MMC in its tracks.
                F24 A(1) UnPause. Starts MMC where it stopped for the Pause.
                F27 A(N) Test counter status: Q=1 if counter is zero
                                              Q=0 if counter is not zero
                F28 A(N) Ditto for motors 17 to 32
                F29 A(N) Ditto for motors 33 to 48
        Reset
                F25 A0, Z*S2 or power ON will clear the motor values and set
                        them all to zero.  No motors will move while this
                        happens.
        Response
                X=1 for all valid commands
                Q=1 or 0 for F27, F28 & F29 (See above)



        MOVING MAGNET CONTROLLER (MMC)                               Page 23-3


        23.2  CONSTRUCTION


        23.2.1  Single-width CAMAC Module


        23.2.2  Front Panel with:

              o  36-pin Amp connector - J1
                         +       -
                         A1      A2      Channel Select bit 1
                         A3      A4         "      "     "  2
                         A5      A6         "      "     "  3
                         A7      A8         "      "     "  4
                         A9      A10        "      "     "  5
                         A11     A12        "      "     "  6
                         B1      B2      Input status - Current > 7A
                         B3      B4        "     "    - Current < 1A
                         C1      C2      Up/Down select
                         C3      C4      Strobe output

        23.3  DRAWING PACKAGE NUMBER

        233-103-00

        23.4  RESPONSIBLE ENGINEER

        M.  Browne / K.  Slattery