



                     Installation Instructions for DIFRAC on a PC
                     --------------------------------------------


        The diskette supplied contains all files necessary to run and maintain 
      the DIFRAC programs on a PC controlling the diffractometer.  These are

         1.  CAD4L.EXE   --  the program to load the interface (CAD4 only).
         2.  DIFRAC.EXE  --  the program to control the instrument;

        The PC should be configured so that 
      a. communication between the computer and the instrument is via COM1:, 
      b. a printer is attached to LPT1: and
      c. graphics is supported with a standard VGA (640x480) card.

        The file GONIOM.INI contains constants needed by program to define the
      diffractometer model, the microscope viewing position, the COM port number and
      baud-rate and, in the case of the CAD4, other constants which define slit
      positions, voltages etc. This file is plain ASCII and commented to facilitate
      editting.


      1.  CAD4L  (CAD-4 only)
          -----
         This is the analogue of the routine of the same name in the original
      Enraf-Nonius control system.  It loads the binary interface code and some of
      the instrumental constants.

         There are three versions of the binary interface code.  

      a. interfaces with Falcon  computers require the file FALCON.EXE;
      b. interfaces with LS-11   computers require the file LSI_11.EXE;
      c. interfaces with Falcon+ computers require the file FALCNP.EXE.

      The routine CAD4L.EXE loads the appropriate file together with the interface
      resident constants from the file goniom.ini.

         The instrumental constants in the file GONIOM.INI should be editted so that
      it contains values appropriate to the instrument in use.  These values should
      be obtained from the original CAD-4 control routine with the CASPAR and GCONST
      commands.

        Files Needed :-- CAD4L.EXE, LSI_11.EXE or FALCON.EXE or FALCNP.EXE,
                         GONIOM.INI.
    

      2.  DIFRAC
          ------
         This is the instrument control routine which carries out all
      crystallographic operations and controls the diffractometer via the interface
      computer.  It too needs the file goniom.ini in order to obtain other
      instrumental constants.  The routine uses the file IDATA.DA to hold all data,
      and if it does not exist when the routine is started it will be created and
      sensible defaults will be supplied for most parameters.

        Files Needed :-- DIFRAC.EXE, GONIOM.INI, probably IDATA.DA.





        Setup Procedure
        ---------------
      1. Create a working subdirectory and copy all files from the diskettes into this
         subdirectory.

      2. Non-CAD-4 machines
         Connect a serial line between COM1: and the instrument interface.
         Edit the file goniom.ini to ensure that it contains at least the correct values
         for Dfmodl, Port, Baud, Vutht, Vuome, Vuchi and Vuphi.

      2. CAD-4 Only
         Before disconnecting the main PDP-11 or VAX computer from the serial line to
         the interface, run the E-N control routine to obtain the instrumental 
         constants for the particular instrument.  Edit the file GONIOM.INI to 
         reflect these constants as well as Dfmodl, Port, Baud, Vutht, Vuome, Vuchi and 
         Vuphi.

         Disconnect the main computer from the interface serial line and connect the 
         line to COM1:.  The connection needs only a straight-through (null-modem)
         cable (2 to 2, 3 to 3 etc).

         Run CAD4L to load the interface.  
         It should not be necessary to perform this step every time the 
         diffractometer is used.  It maybe necessary to turn the interface power off 
         and on again after a few seconds in order to get CAD4L to run properly.  The 
         interface baud-rate is set to 9600 and the routine reports as the 46 blocks 
         are loaded.  If the interface has been loaded correctly, the pocket 
         terminal should be active and displaying the string DIFRAC.  Check that
         the values for HV, LL etc are those from the goniom.ini file.

      3. Run DIFRAC to drive the diffractometer.
         See the writeup for a description of the commands.
         When DIFRAC (and CAD4L) is started a header screen appears from the 
         shareware used to control communication with the serial port.  Follow the
         simple instructions and the screen will clear as the routine is run.


        Files on Diskettes
        ------------------
      1. CAD4L.EXE, LSI_11.EXE, FALCON.EXE, FALCNP.EXE, DIFRAC.EXE, GONIOM.INI.
         Library files GONIO6.LIB and PCL4.LIB.
         CAD4L.MAK and CAD4L.OVL to rebuild CAD4L, and DIF.MAK and DIF.OVL 
         to rebuild DIFRAC, if necessary with Microsoft Fortran.

      2. All source files *.FOR for CAD4L and DIFRAC.  The writeup in ASCII form
         as DIF.ASC and in Word-Perfect 6.1 form as DIF.WPD.
         This file README.DIF.

         It would probably be a good idea to copy all files before using them for any
      other purpose.

        In Case of Difficulties
        -----------------------
        Only 3 problems have been encountered with these programs. 
      1. The cable between the PC and the interface is not a null-modem.
      2. The cable is not connected to the COM1: port.
      3. CAD4L seems to load correctly, but incorrect HV, LL etc values appear in
         the pocket terminal.

        The first 2 problems can be solved by ensuring that the correct cable is
      connected to the correct port.  The third problem occurred in CAD4L and 
      has been fixed.  If difficulties of this type are experienced contact 
      Eric Gabe (e-mail gabe@sg1.chem.nrc.ca).
