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Old 09 October 2019, 23:14   #2

Photon's Avatar
Join Date: Nov 2004
Location: Eksjö / Sweden
Posts: 4,818
You are restoring two copper lists from a structure in OS libraries. In detail: you read longwords from the structures. These are addresses in RAM where the OS copper lists reside - pointers to their starting addresses in Chip RAM.

a6 contains the library base address, and a5 contains the custom chip base address (for reading and writing to hardware registers), and you're using the symbols as offsets from those. COP1LC corresponds to an offset of $80 (128), and COP2LC to $84 (132), as per this hardware register list. So the first line writes to $dff080 and $dff084 in this list, to hopefully restore the screen you were watching before running this program.

Similarly, near the start of your program you might find a write to COP1LC that sets up the screen you want the program to show until exiting.

Last edited by Photon; 09 October 2019 at 23:20.
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