README.TXT for the HC11 based EPROM PROGRAMMER
         ==============================================

Version 1.00   - Programs 2764, 27128 and 27256 EPROMs (12.5v
                 versions only).
               - Read, Verify, Blank Check, Intelligent Blank
                 Check, Download, Memory Dump, etc... all 
                 supported with this version.
               - HC11 internal regs and RAM remapped to allow
                 access to entire 62256 SRAM.
               - This version uses 19.2kbaud only.


1. Print the file "epr_pgmr.ps" in one of the labs.  It's a 
   postscript file of the schematic.

2. Some schematic notes:

   - The whole project can easily be done for $20.  If you have
     enough room on your Micro board, you could put it right on
     there.  Otherwise, make a small daughter-board that hangs off
     of the PIA port.  The board would be about the size of the 
     LED board, so it's quite small.

   - The EPROMs prefer a voltage of about 12.5v for programming.
     Since your EET-110 power supplies do not produce enough
     voltage, a simple 12.7v supply was created on the board using
     a 7812 regulator, a diode and a wall-wart adapter capable of
     delivering anything from +15 to +25 volts (100ma).  Radio
     Shack or Princess Auto probably have something cheap that will
     do the job.  The current Princess Auto catalogue shows a +15v 
     200mA adapter (0720048) for $3.99!

   - If you want, you can eliminate the SPDT switch.  There is
     nothing wrong with reading/writing an EPROM at the high
     voltage, BUT you probably shouldn't insert or remove any
     EPROMs with that power applied (but *I* do).

   - If you plan on using only 27128's you can eliminate the DPDT 
     switch too.

   - It wouldn't hurt to put a small filter cap on the 7812 output.


3. IMPORTANT NOTE: All three types can be read/written with the 
   +12.5v on.  The 2764/27128 additionally can be read/verified/etc
   with the +12.5v off.  The 27256 on the other hand must have the 
   +12.5v on to read or write!!!


4. If you just want to see what it looks like, blast the 
   EPR_PGMR.S19 file into a 27128 using the SuperPro and stuff it
   where Micro11 is.

   The registers and internal hc11 ram are remapped to Bxxx and
   Axxx respectively so that the entire 0000-7FFF is available for
   RAM space to download STUFF to.

5. For example, if you have created the EPR_PGRM EPROM and put it
   where Micro11 used to be, the following commands could be used
   to blast your LAB1.S19 file into EPROM:

   - You must use 19.2 kbaud in PCPLUS.
   - Turn the power off and insert the target EPROM.
   - Turn the power on, and from the Main Menu select,

   - Download
   - Starting Address: C000  (Then send the file using PCPLUS.)
   - Ram Dump                (To check that the code is in memory.
                              The code should start at 0000 and
                              the reset vector should be at 3FFE.)
   - Blank Check             (Or Intelligent Blank Check.)
   - Program
   - Verify
   - Eprom Dump              (If you want to see the EPROM contents)
   

6. Most of the operations are self-explanatory to anyone who has used
   an EPROM programmer.  There is one uncommon command: Intelligent
   Blank Check.  An EPROM programmer can only blast a 1 to a 0 (or 1 
   suppose a 1 to a 1).  To get a 0 to go back to a 1, you must use 
   the UV eraser. This type of blank check is used to determine if an
   already-programmed EPROM can be further programmed.  If the only 
   difference between the RAM buffer image and the EPROM to be 
   programmed is that a few 1's should be turned to 0's, then the 
   programming can proceed without having to erase the EPROM.


7. Suggestions for improvements:  Create Upload and Memory Fill/Modify
   commands.  The actual programming algorithm is currently a single
   1 ms burst.  Any good EPROM data sheet will describe a more thorough
   algorithm which would be a good improvement.


Have fun,
GB