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Old 22 August 2012, 20:57   #56
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Join Date: Dec 2007
Location: Dark Kingdom
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Originally Posted by Wepl View Post
Also my experience: a single custom register access is enough.
I don't would use a cia access because these are slower than custom ones (running on slower clock) and sync is required with custom chips.
yep, a custom register access make sense also because it is Agnus performs it in sequence with the access that cleared INTREQ. It is reasonable to assume that Agnus is designed so that "side effects" of one access (clear INTREQ that propagate to the SR of the CPU) are completed before the following access is performed.
I would also prefer custom access over an access to a CIA register, but there can be cases where it is necessary to access CIA anyway. An example is the interrupt routines for interrupt requests generated by the CIA timers.
So if you first write to INTREQ and then to CIA registers, you are safe without introducing a dummy access to a custom register (like the double write to INTREQ)
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