AOH :: IMG-FMT.TXT|
The .IMG Format
Title : Explanation of .IMG file header
Keywords: XMODEM .IMG FILE HEADER FORMAT
This is a message from our very own deb! describing the .IMG file header
format and how to modify XMODEM protocol terminal programs to accept them.
#: 56956 Sub-topic 7 - Terminal Programs
Fm: CBM Sysop/deb! C. 70007,577
To: Chrisdos 76703,717
Yes, Chris, we know exactly what you need to know.
But I thought *U* were supposed to be the whiz here?????
So, here goes, my tutorial on .IMG files
The first line of an .IMG file looks like this in the INTEL HEX:
^^^^^^ <--- Those 3 bytes are the offset address of the file
^^ <-- That is a null, separating the data from the address
^^^^ <--- That is the number of characters in the .IMG header on the
file, in standard Lo/Hi 6502 format.
(there are 4 bytes in a 64 ID$ header)
^^^^^^ <--- Those 3 bytes are the Commodore 64 ID$ for VIDTEX.
^^ <--- That byte represents whether it is a PRG or SEQ
^^^^ <--- The first actual data bytes from the CBM file
on the disk now show here. You will recognize this as a loading address for a
standard beginning of BASIC file.
Now, in an XMODEM transfer of an IMAGE file, everything after the initial null
delimiter between the offsett address and the header is sent.
Hence, the first character in XMODEM that is sent is $04-EOT for an IMAGE file.
There are six bytes there that are sent and must be stripped off at the
beginning of the download.
Is this perfectlly clear???
P.S. lets put this in a DL somewhere, I get tired of explaining it...
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