On 3/28/2023 3:21 PM, RETRO Innovations via Coco wrote: > That allowed me to filter out all reads of addresses with $df in them, > as a write to $xxfd would be $00fd, where a read would be $01fd. Argh.... A write to $xxdf would be $00df, whereas a read would be $01df Anyway, I hope you got the point. Jim