|
From: | michael osullivan |
Subject: | Re: [Pgubook-readers] indexed addressing mode page 15 (revisited) |
Date: | Thu, 6 Oct 2011 21:23:55 +0100 (BST) |
Hi, I would just like to add to what i said last. What confused me was just why it was mentiond by the author that we should not forget that when we use the value 3 as the index value we will be counting 0,1,2,3 . And next this is how my confused brain processed that little nugget of information: When we jump to a memory address, which is offset by an index value; do we start counting from the address we are already in, or from the next address . Hope i am making sense here., but if we start counting from the address we are at already, a whole word at a time, we arrive at the first byte of the next word. -| if i start counting from the 1st specified address 1 word forward i end up in the .| in the last byte of the word (location 4 below) V_ _ _ _ _ _ _ _ _ _ _ _ _ _V_ _ _ _ _ _ | _ 1 _ | |_ _ 2 _ _| |_ _3_ _ | |_ 4 _ | |_ _5_ _| ...........^ ^-----------------------------------------------------------| ........... | if i however start counting frrom the the next location (location2 here) | i end up in the first byte of the next word (location 5 above) ---------------------------------| Which way is correct? |
[Prev in Thread] | Current Thread | [Next in Thread] |