SPECIAL EPROM's

       There are EPROM's the PROMENADE can read and program but
   which require special methods. Among these are the 27512,
   the 27513 and the 27011. We now consider each of these in
   turn.
       The 27512 is the standard 64k byte EPROM. It has 16
   address pins as can be seen in FIGURE 1. The 16th address
   bit is applied to pin 1. The PROMENADE cannot use pin 1 as
   an ordinary address pin. Rather, it is normally pulled high
   by a pull-up resistor. Some other means must be used to
   bring this pin low for reading and programming the lower 32k
   of the 27512.
        A crude, but simple and effective way to do this is to
   take a short length of 22 gauge stranded hook-up wire and
   ground one end by securing it under one of the PROMENADE
   cover mounting screws. To access the low 32k addresses on
   the 27512, insert the free end of your grounding wire into
   the programming socket along with pin 1 of the 27512. (Pin 1
   is the one closest to the operating lever.) To read or
   program the upper 32k, simply remove the grounding wire.
      Jason-Ranhein Company can install a switch to handle
   this more conveniently for a nominal charge. Contact our
   sales department.
      The 27513 and the 27011 are 'page-addressed' EPROMs.
   They have an internal bank switching register which selects
   one 16k 'Page' of the EPROM at a time. The 27513 looks to
   the outside world like four 27128A EPROM'S; the 27011 looks
   like eight.
      To read or program the 27513, use the control word 4XE2
   where you substitute for X the number from 0 to 3 of the page
   you wish to read or program. For example:

      R2000,5FFF,0,40E2

   will read the lowest 16k page of the 27513 into RAM. Another
   example:

      P4000,7FFF,0,43E2,6

   will program page 3 of the 27513.
      The 27011 works the same way. Use the control word 4X06,
   where X is the number from 0 to 7 of the page you wish to
   read or program.  For example:

      P8000,BFFF,0,4506,6

      This command programs page 5 of a 27011 with data from
   computer RAM from 8000 through BFFF.



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