Posted By
bubis
on 2018-10-29
08:31:55
|  Re: Starting off again
Good progress Doug!
Yeah, you should also treat changes to $fffe-ffff as atomic. I think a good practice is to change some flag (eg. by inc-in some mem) and have some code running in an interrupt to watch that flag and do the appropriate changes.
You can also do your changes between sei/cli but in that case you run the risk of missing/delaying time critical interrupts for example when you have multiple raster interrupts "building" your screen.
I often use this pattern: I have newValueA, newValueB, ... and the flag updateValues. I check in an interrupt if updateValues is zero and if not I copy newValueA, ... to the right place and set updateValues zero again. When I want a change I set newValueA, ... first and inc updateValues.
It is also important that this method is only OK is updateValues never goes above one. That could also cause inconsistent changes when a interrupt happents while your are updating newValues... and updateValues is already non-zero.
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