Partial access to Dual Port mailbox

Question: Does writing or read only to the upper/lower byte (using LB# and UB#) of the mailbox trigger or clear the interrupt flag?

 

Answer:

The mailbox locations in a dual port are the last 2 address locations in the memory.  As long as you are writing to the mailbox address of the Dual Port memory array from the appropriate port, the interrupt flag will become active.  With the same idea, reading only from the upper byte or lower byte of the mailbox from the appropriate port will clear the interrupt flag.