I have a .hex file (flash upgrade) for a special device, running an ARM9 CPU
The firmware allows user to specify a value, up to 247.
The ROM defaults to value of 100, until user enter other value.
But no matter what user enter, it checks that the value is not >247.
The check for >247 - is what I wish to get rid of.
IDA is the tool you'll most likely need to do this job.
The language used to make that ROM was C.