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cbm prg studio
Posted: Tue Oct 24, 2017 7:32 am
by merser
Can someone explain how to load a list of bytes into memory using assembly in cbm prg studio.
I tried *=$1C00
BYTE 126,90,255,189...
I copied the code generated by the SYS call generator tool but the bytes don't load into the location specified when it is run in the emulator.
Re: cbm prg studio
Posted: Tue Oct 24, 2017 4:10 pm
by ajordison
$1C00 is in the BASIC area, so BASIC itself might be over-writing your bytes. What are you trying to do?
Re: cbm prg studio
Posted: Wed Oct 25, 2017 6:48 am
by merser
Hi,
I am copying the character set to top of ram and modifying. I just want to know an easier way of loading the modified character data into memory.
Thought I could do that with the byte statement but it doesn't appear to work. However if as you can see I do a series of loads and stores the data is there.
Code: Select all
; 10 SYS (6968)
*=$1001
BYTE $0E, $10, $0A, $00, $9E, $20, $28, $36
BYTE $39, $36, $38, $29, $00, $00, $00
*=$1C00
byte 126, 90, 255, 189, 189, 36, 66, 36
CHAROM_START = $8000
CHARAM_START = $1C00
SCREEN_START = $1E00
*=$1B38
lda #$93
jsr $FFD2
ldx #$0
Char_Copy
lda CHAROM_START,x
sta CHARAM_START,x
lda CHAROM_START,x + $100
sta CHARAM_START,x + $100
inx
bne CHAR_COPY
New_Char
lda #126
sta CHARAM_START
lda #90
sta CHARAM_START + 1
lda #255
sta CHARAM_START + 2
lda #189
sta CHARAM_START + 3
lda #189
sta CHARAM_START + 4
lda #36
sta CHARAM_START + 5
lda #66
sta CHARAM_START + 6
lda #36
sta CHARAM_START + 7
Char_Pointer
lda #$FF
sta $9005
Print_Char1
lda #$40
jsr $FFD2
End
rts
Re: cbm prg studio
Posted: Fri Oct 27, 2017 4:00 pm
by merser
OK so I figured out what I did wrong. The BYTE instruction was loading my custom character data into 7168-7175 at the start but then was copied over by the CHAR_COPY routine. Once I changed the starting address CHAROM_START and CHARAM_START to start after the loaded custom character data it worked.