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Z80 & 68k Assembly =>
z80 & ez80 Assembly
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Jeffrey
Member
Joined: 12 Jun 2003
Posts: 212
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 Posted: 25 Oct 2003 08:07:04 pm Post subject: |
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OK, i can create AppVars, but I cant edit or use them in a program. My ulitimate goal (thanks to Justin W) is to make an asm formula bank that will have a formula editor with it.
So, how do I do the appvars? |
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Justin W.
Shattered Silence
Advanced Member
Joined: 24 May 2003
Posts: 429
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| Posted: 26 Oct 2003 12:36:49 am Post subject: |
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OK Appvars are rather simple.
To access their data you use the ChkFindSym ROM Call to get the appropriate pointers to the appvars data.
Note: This code is to be used if the appvar you are trying to access already exists.
Code:
ld hl,AppvarName
rst 20h
bcall(_ChkFindSym);de=pointer to data in ram hl=pointer to symbol table entry
ret c ;If the appvar doesn't exist return
inc de
inc de;by incrementing de twice we have bypassed the size bytes of the appvar
;-----here you can read or write data to and from the appvar
AppvarName:
.db AppVarObj,"TestVar",0
I hope this helps you out Jeffery. |
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Jeffrey
Member
Joined: 12 Jun 2003
Posts: 212
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| Posted: 26 Oct 2003 09:36:56 am Post subject: |
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Ok, so to write to the AppVar itself, would you do like:
Code:
ld hl,stufftoput
ld (de),hl
stufftoput:
.db "Test Text",0
Then how would I read from it? |
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Justin W.
Shattered Silence
Advanced Member
Joined: 24 May 2003
Posts: 429
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| Posted: 26 Oct 2003 11:13:58 am Post subject: |
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Jeffrey wrote: Ok, so to write to the AppVar itself, would you do like:
Code: ld hl,stufftoput
ld (de),hl
stufftoput:
.db "Test Text",0
Then how would I read from it?
Actually your code above would not work.
ld (de),hl is not a legal z80 instruction. Even if it was all that would do is load the address of the text string into de.
If you wanted to copy that string into the appvar you would need to
Code:
;Note-de already is at the address we want to copy to, so don't change it.
ld hl,stufftoput
ld bc,10 ;10 being the length of the string
ldir ;copy the bytes
;whatever code--------
stufftoput:
.db "Test Text",0
The above would copy the entire 10 bytes of the string stufftoput to the appvar.
Now let's say you wanted to read from the appvar then write the data to a saferam buffer.
Now let's assume that you have just used the code in my first post to get to the start of the appvar's data. Immediately following the 2 inc de's
Code:
ex de,hl ;swap hl with de so hl is now pointing to the start of the appvars data
ld de,AppBackUpScreen ;768 bytes buffer for use by asm programs and apps
ld bc,10 ;10 bytes to copy as before
ldir ;copy the bytes
Now that's to do multiple byte writing and reading.
Let's say you want to read a single byte from the appvar. Once again assume that we have just done the ChkFindSym routine in the first post.
Code:
ld a,(de)
;here you can do whatever you want with a as it holds the first byte of the appvar
Last edited by Guest on 26 Oct 2003 11:16:27 am; edited 1 time in total |
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