[Coco] Assembly timing question
mechacoco at gmail.com
Mon Mar 21 23:37:11 EDT 2016
On Mon, Mar 21, 2016 at 7:53 PM, Lee Patterson wrote:
> Looking at 6809 Assembly Language Programming by Leventhal, and trying to
> figure out cycle counts. Addressing modes
> 1) What addressing mode is LDA ,X+ using? I think it's extended direct
> addressing, which is 5 cycles.
> 2) leay 1,y is listed as 4+ cycles. How do I know how many the "+" is?
Both of those instructions use Indexed addressing. There are several
variations of Indexed addressing. LDA ,X+ is the 'post-increment by 1'
variation, while LEAY 1,Y would assemble as the '5-bit offset,
The "+" appears in the cycle count column because you need to add the
number of cycles associated with the particular Indexed variation to get
the total cycle count. There should be a separate Indexed Addressing Mode
Table which lists the additional cycle counts (and byte counts) for each
More information about the Coco