8259 Interrupt Controller OCW2 register

Jan 26, 2008 0 Replies

Hi all,



I am trying to figure out how an 8259 OCW2 register behaves, more specifically if the "Automatic Rotation" bits of OCW2 are latched or not.



For example, if I want to automatically rotate interrupt priorities on a Non-Specific EOI, do I



a) Issue a "Rotate on non-specific EOI command" to OCW2 during initialisation and then issue a Non-Specific EOI at the end of my ISR.



or



b) I issue a "Rotate on non-specific EOI command" at the end of my ISR.



Thanks Hans.


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