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lovebyte2023: one more update to README
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@ -60,8 +60,8 @@ values from uninitialized RAM at boot
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usually aren't useful.
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usually aren't useful.
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You can try drawing directly to screen
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You can try drawing directly to screen
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memory at addresses $2000 (PAGE1)
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memory at addresses $2000* (PAGE1)
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or $4000 (PAGE2), but that takes
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or $4000 (PAGE2) , but that takes
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3 bytes and if you want to draw to
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3 bytes and if you want to draw to
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all 8K of the screen you need to
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all 8K of the screen you need to
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have a way to increment a 16-bit
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have a way to increment a 16-bit
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@ -80,6 +80,10 @@ change the color.
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So is all hope lost?
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So is all hope lost?
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* note a leading $ is how you
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traditionally indicate hexadecimal
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numbers on 6502 computers
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=== THE CHRGET TRICK ===
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=== THE CHRGET TRICK ===
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We can use a trick I found in a
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We can use a trick I found in a
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@ -201,10 +205,10 @@ effects. An obvious choice would
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be the no-operation NOP instruction,
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be the no-operation NOP instruction,
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which is $EA. Convenient, as $EAEA
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which is $EA. Convenient, as $EAEA
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points nicely into the ROM. It turns
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points nicely into the ROM. It turns
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out there are some fun* complications
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out there are some fun** complications
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with doing this.
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with doing this.
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* As per 4am, no fun is actually
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** As per 4am, no fun is actually
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guaranteed in this process
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guaranteed in this process
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=== WHEREIN WE GET A BEEP AND ===
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=== WHEREIN WE GET A BEEP AND ===
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@ -226,7 +230,7 @@ The problem here is BKGND0 assumes the
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value of the first page of graphics
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value of the first page of graphics
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you want to fill is in zero-page
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you want to fill is in zero-page
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location HGR_PAGE ($E6). On bootup
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location HGR_PAGE ($E6). On bootup
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this is likely uninitialzed (it
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this is likely uninitialized (it
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often ends up $00 or $FF), so when
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often ends up $00 or $FF), so when
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you call the routine it happily writes
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you call the routine it happily writes
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your color pattern across the first 8k
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your color pattern across the first 8k
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