[aprssig] Re: Dual Configurations in EPROM

WA8LMF2 at aol.com WA8LMF2 at aol.com
Mon May 23 08:31:39 EDT 2005

mcheavens at usa.net wrote:

> I am looking for a utility or how-to for loading two configurations. (KISS 
mode and Ui-Digi) into a single 27C512 and use the hi/lo pin 1 configuration 
> I am tired of switching and having to keep multiple roms at sites for 

Many utilities that come with eprom programmers can do this quite easily.

1)   Most programming apps read the data for the prom being programmed into 
RAM  before blowing the eprom.  Set the programming utility to program a 
27C512.  This assigns a RAM buffer the size of a 27512.  You read the first 
27256-sized file into RAM and tell the programming utility to load it at offset 0000 
Hex (the start of the first half of the RAM buffer) .  Then read in the second 
27256-sized file and tell the utility to load it at offset 8000 Hex (the 
beginning of the the upper half of the RAM buffer).  This will stack the the two 
eprom images into the lower and upper halves of a 27512-sized buffer 
respectively.   Then blow the entire prom in one pass.

--- or ---

2)  Some eprom apps allow you to program only part of an eprom at a time if 
you want.  If you have this kind of programming utility, read the first file 
and tell the programmer to blow 8000 H bytes starting at 0000 H.     Then tell 
the programmer to read the second file and blow 8000 H bytes starting at offset 
     Or it may be expressed as start and end addresses instead of start 
address and length. In this case, tell the programmer to program the first file 
between 0000 H and 7FFF H, and to then program  the second file between 8000 H 
and FFFF H.

--- or ---

3) Combine the two image files into a single larger one.  This can be done 
either by opening the files in a hex editor (or even Wordpad if you are 
careful).  Select all of the file open in one instance of the editor, copy it and 
paste it at the very beginning (or end) of the second file. Then save it   Or you 
can use the classic DOS copy  command:

    COPY  /b    Filename1.bin+Filename2.bin    Filename3.bin   

where Filename1.bin  and Filename2.bin are the original UI-DIGI file and the 
original TNC prom file while Filename3.bin is the combined file that I usually 
name DoubleDecker.bin .   This command will combine ("concatinate") two or 
more files into a single larger file.    Then just blow a single pass using a 
27512-sized file directly into a 27C512 with no offsets or segmenting required.

Once you have the 27512 eprom ready to install, bend pin  one so it misses 
the socket when the prom is inserted into the socket.  Connect pin 1 to a 
single-pole double-throw toggle switch so that you can either ground pin 1 or apply 
5 VDC  to it.    I usually use an E-Z-Hook micro-grabber  test lead to snag 
the pin (instead of soldering to it) so I can easily remove the chip when needed.

Stephen H. Smith             wa8lmf (at) aol.com
Home Page:                   http://wa8lmf.com

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