Hi Fhub,


You can put the good byte for a good checksum at the end of the patch.
However, a curious programmer (Fh..) could be astonished by a byte never adressed by the patch.

So I prefer to use a dummy short instruction (yes, with 2 clocks CPU lost) with the good byte as immediate value.
The BF is a "branch never", as BT is a branch always, without testing any code condition.
So 41 50 is a 2 clocks cpu lost instruction who only make PC = PC+2, and 50 is the byte for a good checksum.

You can make a best performance patch with :

66D0: 7F52 7260 bclr #6, @h'ff52
66D4: 7F52 7270 bclr #7, @h'ff52
66D8: 5A00 5062 jmp h'5062
66DC: 91 ; (41+50)

Cordialy,

Mychess