Instruments supported by V9.7 firmware:

   494A/P
   492A/P
   492B/P
   492PGM
   495/P
   497/P
   2753
   2754
   2755/A
   2756

Note: The 497/P and 494A/P analyzers are physically very similar instruments,
possibly identical.  However, the signal-counter feature is disabled in the 
497/P's firmware, at least in serial numbers after B020000.  It is possible 
to restore the counter functionality by resetting the 497/P's DIP switches to
'fool' the firmware into thinking it's installed in a 494A/P.  To do this --
or to install the 9.7 ROMS in a 494A/P -- set the DIP switches for "494A/P" 
in the table below:

         Memory board        Z-axis board
         ------------        -------------
495/P:   4 open              2,3,5,7 open; 1 closed for P-suffix version
494A/P:  3 open*             2,3,4,5,6,7 open; 1 closed for P-suffix version**
497/P:   2,3,4 open          3,4,6,7 open; 1 closed for P-suffix version
492B/P:  1,2 open
492A/P:  2 open

*: 2 open for 1 MHz filter, closed for 3 MHz
   1 open if 10/100 Hz filters not present
   1,2 open if 100 Hz filter present but not 10 Hz

**: 6 open for 100 kHz filter, closed for 300 kHz
    2,3,4,5,7 = unknown function (7 possibly Opt 07 for 75-ohm compatibility)

These switch settings were determined by empirical observation.  Some 
experimentation may be necessary depending on the options installed
in the instrument.

When using the 494A/P switch configuration in a 497/P, the instrument will
identify itself as a 494A/P during bootup and GPIB operations.  To remedy this,
the ROM image for 160-8318-00.BIN may be replaced with 
160-8318-00-494AP_renamed_to_497P.bin.  The two ROM images are identical 
except that the '494A' identification text has been replaced with '497' in 
the latter image.

These files should be burned to 27256-3 or faster EPROMs.

John Miles (jmiles@pop.net)
21-May-04