26 July 2024, 08:45 | #1 |
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Clearing bits in ciaicr mask
Does clearing bits in a ciaicr mask - e.g. move.b #CIAICRF_TB,(_ciaa+ciaicr) - immediately mask them if they are already set (i.e. when the register is next read)? I want to reset a bit in the icr without affecting other bits that may already be set. I can't just read ciaicr to clear it because that clears the entire register.
Perhaps it is a moot point, since if an interrupt is signalled to ciaicr and I have a ports interrupt installed, then I would expect the interrupt to occur before my code is setting ciaicr elsewhere. So it might be a redundant question. Last edited by DJ Mike; 26 July 2024 at 09:00. |
26 July 2024, 09:23 | #2 |
Defendit numerus
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icr contains two registers at the same address, one read-only and one write-only.
They are completely separate. So even if you write a specifica mask, when you read the register it will contain the 'historical situation' of the interrupt requests, even those that were instantly masked. This means that if you have pending interrupts, they remain pending after writing. |
26 July 2024, 09:43 | #3 |
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Thanks for clarifying ross. That's helpful to me to be aware of. Thankfully I don't think it materially impacts what my program is doing.
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