VTC Error Checks
                           --------------------

                                                        Rev.  17-MAR-1993


Some checks for Error Conditions can be added to the VTC.  This will help
seperate problems that happen as the Data Block is being built from
problems that happen later.  The checks that can be made include:

1. Verify that the Beam Crossing Number that is read early in the COMINT
   PROM's matches the Beam Crossing Number that is read at the very end of
   the COMINT PROM's.

2. Verify tha the List of Spec Trig's Fired that is read near the front of
   the COMINT PROM's matches the List of Spec Trig's Fired that is read
   very near the end of the COMINT PROM's.   The Spec Trig's Fired List
   that is build from the reads near the begining of the COMINT PROM's is
   based on data from the 1st section of the Spec Trig's Fired IMLRO.
   The read at the end of the COMINT PROM's is from the 3rd section of this
   IMLRO so we are also testing for consistency in the various sections of
   the Spec Trig's Fired IMLRO.

3. Verify the the Current Beam Crossing Number is equal to the Previous
   Beam Crossing Number plus 1.


How to flag an error when one is found:

  We can not tie up the system putting lots of characters to the screen
because this will cause trouble for L2.  VTC could put out a carriage
return and a 2 character error code (i.e. 4 characters total) and then
maintain a counter that is only displayed during the  "Monitor Data Only
Event Not Transfered" message.   We could try to do screen management and
always display the error counts at the bottom of the screen but I think
that it takes a lot of characters to do this.

Recall that any character I/O that is done will need to use the Private
routines in  ASCII_Routines.SRC  and not calls to the 133A Bug Monitor.


What needs to change in the VTC program structure:

  The basic idea is to include a new module called, "Error_Checking_1.SRC".
i.e. the error checking will not be scattered through out a number of
modules but rather it will all be contained in one module.

The following COM files will need to pick up a reference to
Error_Checking:

       BUILD_VME_TRANSFER_PROGRAM
       CHECK_DIFFERENCES_IN_VTC_1
       COPY_VTC_1.COM

The OPT file will need to pick up a reference to Error_Checking:

       VTC_1.OPT

The global symbols will need to be included in :

       Main_Symbols.Include

The calls to run Error_Checking will need to be added to:

       Cycle Master_1.SRC



Original version of Error Checking from 17-MAR-1993:

  This included only the carriage return and the 2 letter code sent to the
VTC console to flag each of the error type.  In addition the error code "JL"
which flags an empty Jet List has included the 8 hex digits to indicate
the List of Spec Trig's that have Fired for this event.

  In this version no counters are kept of the total count of each type of
error.

  For the future, we could include the ability for the VTC to write a log
file on the host VAX.  It could do this over the RS232 link that is used
to load the program into the VTC.  It could use commands like:

              Copy/Append   TT:   [TrgUser.  ]VTC_Log_File.Txt
              Text of the Log Message
              Control Z

These could include a time stamp because the VTC knows the absolute time
and can make an ASCII character string out of it.  A version limit could
be set on the log file on the VAX to control its growth.

The serial port on the MVME-133A that is connected to the VAX is call
Port B.  It is driven by Port B of a Z8530 UART (Zilog, AMD).  Appendix C
of the MVME-133A book shows examples of using the Z8530 serial Port B.
Sheet 19 of the schematic section of the MVME-133A manual covers the Z8530
setup.

The MVME-133A module is setup so that the Z8530 appears at the following
addresses.  Note that the Z8530 is refered to as the SIO.

                   SIO Function            Address
            -------------------------    -----------
             SIOB RRO,  SIOB WRO           FFFA0000
             SIOB RXDATA, SIOB TXDATA      FFFA0001
             SIOA RRO,  SIOA WRO           FFFA0002
             SIOA RXDATA, SIOA TXDATA      FFFA0003


How does the Bu-133A have/need Port B setup?

Who echos the characters sent out Port B during Bug-133A transparent mode
operation?  If Port B itself is doing the echos then our Log-File messages
may be echoed and cause received character interrupts.