Thank you Sorunome, but I'm afraid that's not the problem. I got the interrupt setup method I used from http://tutorials.eeems.ca/ASMin28Days/lesson/day23.html, which explains that the lowest 6 bits of the data bus are always set when calling a mode 2 interrupt. There may be a catch to this, but the fact that the pixels were displayed as intended in my original program shows that the interrupt was called correctly.

So, I've been trying to learn assembly as of late, and a few days ago I started messing around with interrupts. However, I could never get the programs to work as intended, and corrupted the calculator's system routines accidentally whilst trying to do so. (I'm on vacation without my link cable and writing the code on-calc with Mimas)  Forced to use direct output rather than putS to figure out what was going on, I wrote this program.
  di
  ld a,$99
;setting up interrupt
  ld i,a
  ld hl,Interrupt
  ld ($993F),hl
  ld ($997F),hl
  ld ($99BF),hl
  ld ($99FF),hl
  im 2
  ld e,$FF
  ei
Loop:
;Infinite loop o' ram clears
  jr Loop
Interrupt:
  ld a,26
;setting column
  out ($10),a
  call WasteTime
;my equivalent of _LCD_BUSY_QUICK
  ld a,$96
;setting row
  out ($10),a
  call WasteTime
  ld a,e
;displaying e as row of pixels
  out ($11),a
  dec e
  reti
WasteTime:
  ld l,10
WasteLoop:
  nop
;344 T-states, just to be safe
  nop
  nop
  nop
  dec l
  jr nz,WasteLoop
  ret
The expectation here is that every 140th of a second, the row of pixels specified would update to reflect e. I understand that the LCD has a refresh rate of 60 fps, but the row of pixels should update on some interval. However, instead, only a solid row of pixels (reflecting e's original $FF) is displayed, which never changes. Since the pixels were displayed at the correct coordinates as intended, I'm reasonably certain that the interrupt setup is working, and that WasteTime is functional as well. That narrows it down to these two lines:
dec e
reti
And I'm pretty sure I know how dec works . Is there something I don't understand about reti? Or is there something entirely different wrong with my understanding of assembly? Sorry for the long post, I wanted to give as much information as possible.

Thanks in advance!


Edit Sorunome: added code tags

 
 

Thank you very much for the help! Since all the files involved do not fit in ram, I'll download Doors CE. If I am still unable to run the program, I'll inquire further on codewalr.us