Rockwell Automation Allen-Bradley ControlLogix 1756-MVI Programming Reference Manual page 129

Typically, plan on an extra 10KB for system overhead. Also plan
on additional wasted bytes at the end of each file, since files are
allocated on the disk in units of clusters, not individual bytes.
For 1.44 MB floppies, one cluster equals one sector (512 bytes),
so the maximum waste per file is 511 bytes.
2. Copy the files you want to the floppy.
TIP
3. Run DISKIMAG on the floppy to create a file that contains its
image, or the first portion of the floppy. DISKIMAG is run from
the command line with three arguments, as follows:
DISKIMAG d: filename [kb_to_copy]
The d: operand specifies the drive letter from which to read raw
sectors. This must be A: or B:
The filename operand specifies the name of the output file to
copy the raw sectors into as a contiguous byte stream.
The kb_to_copy operand specifies the number of kilobytes (1024
byte units) of data to transfer from the floppy. Note that 1K is
two sectors for 512-byte sectors. The size specified here cannot
exceed the maximum size of the MVI module ROM disk (896K).
For example, to copy 360KB from your drive B: to a file called
OUTPUT.BIN, use the following command:
DISKIMAG B: OUTPUT.BIN 360
As another example, if you have some files on a 1.44MB 3.5"
diskette that you need to turn into a 96KB ROM disk, then you
would use the following command:
DISKIMAG B: OUTPUT.BIN 96
Programming the MVI Module
If you need to change the contents of the
floppy, re-format the disk, then copy the
desired files. Do not simply delete unwanted
files from the floppy, as this will cause disk
fragmentation and will waste ROM space.
Publication 1756-RM004B-EN-P - October 2000
6-5