03-05-2013, 05:33 PM
Hi all
I'm starting to learn how to manipulate screen directly at memory address level. Right now, I'm messing with this code
Questions are:
- Are there any better options to read and write given a X and Y coordinates?
- What is the best way to storage screen memory addresses and their values? Integer (for addresses) and Ubyte (for values) arrays, right?
Thanks and regards
I'm starting to learn how to manipulate screen directly at memory address level. Right now, I'm messing with this code
Code:
rem screen values
paper 0: border 0: ink 7: cls
dim conta as byte
dim x,y,n,adres,dirb as uinteger
bucle:
y=RND*10
x=RND*32
adres=0
POKE attrAddress(x,y),RND*256
Print at 10,0; "X="; x; " - "; "Y="; y;
print at 11,0; "Attrib address is.......: "; attrAddress(x,y);
print at 12,0; "Attrib value is.........: "; PEEK attrAddress(x,y);
print at 13,0; "The 8 screen addresses..: "
for conta=0 to 7
poke scrAddress(x,y)+adres,RND*256
print scrAddress(x,y)+adres;","; PEEK (scrAddress(x,y)+adres)
adres=adres+256
next conta
pause 0
cls
goto bucle
rem funciones
FUNCTION scrAddress(x AS UBYTE, y AS UBYTE) AS UINTEGER
ASM
; This FUNCTION returns the address into HL of the screen address
; x,y in character grid notation.
; Original CODE was extracted by BloodBaz
; x Arrives in A, y is in stack.
AND 31
ld l,a
ld a,(IX+7) ; Y value
ld d,a
AND 24
add a,64
ld h,a
ld a,d
AND 7
rrca
rrca
rrca
OR l
ld l,a
END ASM
END FUNCTION
FUNCTION attrAddress (x AS UBYTE, y AS UBYTE) AS UINTEGER
'This function returns the memory address of the Character Position
'x,y in the attribute screen memory.
'Adapted from code by Jonathan Cauldwell.
'Rebuilt for ZX BASIC by Britlion from NA_TH_AN's fourspriter, with permission.
ASM
ld a,(IX+7) ;ypos
rrca
rrca
rrca ; Multiply by 32
ld l,a ; Pass TO L
AND 3 ; Mask with 00000011
add a,88 ; 88 * 256 = 22528 - start of attributes.
ld h,a ; Put it in the High BYTE
ld a,l ; We get y value *32
AND 224 ; Mask with 11100000
ld l,a ; Put it in L
ld a,(IX+5) ; xpos
add a,l ; Add it TO the Low BYTE
ld l,a ; Put it back in L, AND we're done. HL=Address.
END ASM
END FUNCTIONQuestions are:
- Are there any better options to read and write given a X and Y coordinates?
- What is the best way to storage screen memory addresses and their values? Integer (for addresses) and Ubyte (for values) arrays, right?
Thanks and regards
