Then I should save SP's initial address at the beginning of the prog and restore it at the end? That makes perfect sense.

No... You should just not pop without pushing, and you shouldn't do math operations on the SP at all.. Remember, if you screw with the SP, all the calls and rets will be messed up, too

Seriously, go read the tutorial on it rather than asking questions that are answered *gasp* IN THE TUTORIAL

C9 = ret, and I assume D1 = pop de.

Ah, I didn't get too much sleep; I don't think I actually looked at what the numbers were. I just noticed it was 4 nibbles and went from there.

Ok, I've solidly memorized the first 256 opcodes. I fully understand them all except for DAA, which I can't find good documentation for. Is it something I should know about?

Edit: Never mind, I just found a place that described it well. It sucks.

Actually, it can be very useful. I used it in GSM for the timer.

GSM?

Shorthand for Grayscale Minesweeper

Oh. I thought it would be something like "Grassembly".

I personally thought it was Global System for Mobile Communications.

its that too :p

Really? How?

I used daa to keep it in "decimal" so I wouldn't have to divide by 10 repeatedly to get the digits, that would delay a lot (relatively).

This makes no sense to me! I've gone over my code, but I can't find a reason for this happening. It's supposed to output 2 8x8 bitmaps (one shaded, one not) at the third LCD row and then loop endlessly on a grayscale square in the top-left hand corner of the screen. Instead, I get rectangles everywhere, the run indicator moves to the center of the screen (along with another black rectangle), and the gs square is really flickery. If anyone has free time they'd like to devote to helping me out, I'd be that much happier. Here's the code:
Code:

or (I hope I don't mess up):
Code:

I know it's horribly unoptimized, but the use for my drawing subroutine will vary slightly as the program progresses (I'm not near done with it).

If the greyscale is flickering, it's because of your picture data.

use:

.db %10101010
.db %01010101

instead of:

.db %11111111
.db %00000000

I've heard of doing that, but is it just to compensate for the inconsistency of the calc's LCD?

Never mind with the other problems; it looks like I've just forgotten to disable interrupts.