« previous next »
Pages: [1]   Go Down

Author Topic: Page Swapping  (Read 3648 times)

0 Members and 1 Guest are viewing this topic.

SirCmpwn

  • Guest
Page Swapping
« on: March 18, 2011, 07:39:30 pm »
This is my entire code:
Code: [Select]
di
ld a, $82
out (7), a
ld a, $81 ;also tried $80
out (7), a
ei
ret
This crashes, any idea why?

EDIT: I'm a dork :P perhaps I shouldn't be executing in the 0x8000-0xC000 when I swap it out.
« Last Edit: March 18, 2011, 08:02:35 pm by SirCmpwn »
Logged
+1/-0 karm for this message

Offline jnesselr

  • King Graphmastur
  • LV11 Super Veteran (Next: 3000)
  • ***********
  • Posts: 2270
  • Rating: +81/-20
  • TAO == epic
    • View Profile
Re: Page Swapping
« Reply #1 on: March 18, 2011, 09:58:54 pm »
that would be a good idea.  Just to clarify to anyone who's reading and has the same problem, port 7 controls the ram page that is located in the 0x8000-0xC000 range.  When you swap the page out, pc still points to whatever location inside there, and so points to the new page and not the old one.

I had the same issue for multipage apps.
Logged

Offline ZippyDee

  • LV8 Addict (Next: 1000)
  • ********
  • Posts: 729
  • Rating: +83/-8
  • Why not zoidberg?
    • View Profile
Re: Page Swapping
« Reply #2 on: March 28, 2011, 07:18:54 am »
So how does one deal with that issue?
Logged
There's something about Tuesday...


Pushpins 'n' stuff...

Offline jnesselr

  • King Graphmastur
  • LV11 Super Veteran (Next: 3000)
  • ***********
  • Posts: 2270
  • Rating: +81/-20
  • TAO == epic
    • View Profile
Re: Page Swapping
« Reply #3 on: March 28, 2011, 07:34:15 am »
Quote from: ZippyDee on March 28, 2011, 07:18:54 am
So how does one deal with that issue?
Well, you place code outside of the page you are moving to move it.  For example, in an app that's stored from $4000-$7FFF, you could place a routine in ram at $8000 that swaps the pages out.  This is essentially what bcall does, albeit with a table lookup routine and other stuff.  bcall is on page 0 at a set location, and it can therefore swap any page out of any bank, because it can't be swapped out.

TL;DR, you have to have a routine outside of the page you are trying to swap.
Logged

Offline thepenguin77

  • z80 Assembly Master
  • LV10 31337 u53r (Next: 2000)
  • **********
  • Posts: 1594
  • Rating: +823/-5
  • The game in my avatar is bit.ly/p0zPWu
    • View Profile
Re: Page Swapping
« Reply #4 on: March 28, 2011, 09:16:48 am »
For a really easy way that will work on all calculators. Output $81 (Ram page 1) to port (06) ($4000-$8000). Then jump to a [label in you program - $4000]. You are now executing in the $4000 range so you can do whatever with port (07). Then when you are done, put page $81 back into (07) and jump back.

Remember though, when you are executing in the $4000's, all the labels in your program are still back up in the $8000 range. So anything that requires an absolute address: jp; ld hl, (label in your program); and call; all need to be adjusted accordingly when you switch.
Logged
zStart v1.3.013 9-20-2013 
All of my utilities
TI-Connect Help
You can build a statue out of either 1'x1' blocks or 12'x12' blocks. The 1'x1' blocks will take a lot longer, but the final product is worth it.
       -Runer112

Offline jnesselr

  • King Graphmastur
  • LV11 Super Veteran (Next: 3000)
  • ***********
  • Posts: 2270
  • Rating: +81/-20
  • TAO == epic
    • View Profile
Re: Page Swapping
« Reply #5 on: March 28, 2011, 05:05:05 pm »
note that the post above refers to if you use an asm program only, and not an app.
Logged

Offline DrDnar

  • LV7 Elite (Next: 700)
  • *******
  • Posts: 546
  • Rating: +97/-1
    • View Profile
Re: Page Swapping
« Reply #6 on: March 28, 2011, 05:26:02 pm »
Why don't you just swap in the 4000h-7FFFh range (port 6). It's what EOS uses itself. (Though that won't work for applications, in which case your code is fine, but only for applications.)
Logged
"No tools will make a man a skilled workman, or master of defense, nor be of any use to him who has not learned how to handle them, and has never bestowed any attention upon them. . . . Yes, [] the tools which would teach men their own use would be beyond price."—Plato's The Republic, circa 380 BC

Offline Compynerd255

  • LV6 Super Member (Next: 500)
  • ******
  • Posts: 336
  • Rating: +53/-4
  • Betafreak Games
    • View Profile
    • Betafreak Games
Re: Page Swapping
« Reply #7 on: March 28, 2011, 05:33:38 pm »
What's the hex for storing ports? I'd like to try this page switching thing in Axe.
Logged
The Slime: On Hold, preparing to add dynamic tiles

Axe Eitrix: DONE

Betafreak Games: Fun filled games for XBox and PC. Check it out at http://www.betafreak.com


Offline jnesselr

  • King Graphmastur
  • LV11 Super Veteran (Next: 3000)
  • ***********
  • Posts: 2270
  • Rating: +81/-20
  • TAO == epic
    • View Profile
Re: Page Swapping
« Reply #8 on: March 28, 2011, 05:37:08 pm »
Quote from: Compynerd255 on March 28, 2011, 05:33:38 pm
What's the hex for storing ports? I'd like to try this page switching thing in Axe.
D3 is out, so D306 would be out (6),a.  ld a,* is 3E, so ld a, $FF would be 3EFF.  So to swap page 81 into the $4000 region, you would do 3E81D306.  More of these equates can be found here.
Logged

Offline FloppusMaximus

  • LV5 Advanced (Next: 300)
  • *****
  • Posts: 290
  • Rating: +57/-5
    • View Profile
Re: Page Swapping
« Reply #9 on: March 28, 2011, 11:12:10 pm »
Points to keep in mind:
- If you alter the mapping in the 8000-BFFF or C000-FFFF blocks, system routines - including the system interrupt service routine - will not work.  Most other stuff - e.g., shell library routines, many Axe builtin commands - won't work either.
- If you alter the mapping in the 4000-7FFF block, you must restore the original mapping before exiting your program.
Logged
Pages: [1]   Go Up
« previous next »