User`s manual

Chapter, 9, Using DEBUG.COM
You may use DEBUG.COM (supplied with DOS) in conjunction with
our GHEX.EXE to modify an INTEL.HEX file without worrying about
the checksums in the INTEL.HEX file.
The following is a short tutorial to modify a 4K byte INTEL.HEX file with
DEBUG. The procedure is to run DEBUG first.
C>DEBUG<cr>
—_
From the – prompter within DEBUG use the N command to specify the
name of your INTEL.HEX file.
—Nfilename.HEX<cr>
—_
Use the L command to load the hex file with an offset (if it begins at
0000H). You must do this since if it starts loading at 0000H within the
segment, it will overwrite your file control block at 5Ch.
—L 100<cr>
—_
The CX register now contains the number of bytes read into memory
with an offset of 100. You may have to modify the CX register to
properly reflect the correct number bytes you must write back to the
disk. Remember that this is going to write from CS:CX when you issue
the command.
—RCX<cr>
CX: 1000<cr>
—_
Your data is now loaded into the memory of the computer at offset
100H. Use the E command to modify the bytes you need to modify. An
example of modifying locations starting at 0A55H with data is shown.
Locations A55H through A57H contain FFH.
—EA55 01 02 03<cr>
—_
Now specify a new file name to write to the disk with since you can’t
use an extension of HEX with the file you are writing. You want to call
it a BIN or IMG file instead since that is what the data really is anyway.
Model 9000 Debug.Com Chapter 9
Page 33