add more explanations of common instruction sequences
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@@ -0,0 +1,6 @@
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End of routine followed by $00 -> ZP location
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$60 = RTS = return from subroutine. Very common.
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LDA #$00 / STA $xx is also very common.
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It is no suprise to find these together many times in code.
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Not copyrightable.
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STA $DC00 instruction
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Single instruction. Not copyrightable.
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STA $DD00 instruction
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Single instructions are not copyrightable.
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STA $DC04 instruction.
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Single instruction. Not copyrightable.
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STA $DC04 / LDA #$xx sequence
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This is a single instruction with the opcode of a very common
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instruction (LDA #$xx) following. Not copyrightable.
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STA $DC05 instruction
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Single instruction. Not copyrightable.
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STA $DC0E instructioon
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Single instruction. Not copyrightable.
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STA $D011
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Single instructions are not copyrightable
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STA $0200,Y instruction
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Single instruction. Not copyrightable.
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Store $00 to a ZP location
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LDA #$00
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STA $xx
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Obvious way to do this, so not copyrightable.
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Store $00 somewhere
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LDA #$00
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STA $xxxx
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This is an obvious way to put $00 into a memory location
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Store $01 to a ZP location
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LDA #$01
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STA $xx
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Obvious way to do this, so not copyrightable.
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Put $03 into ZP location
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LDA #$03
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STA $xx
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This is the obvious way to put $03 into a ZP memory location.
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Store $08 somewhere
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LDA #$08
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STA $xxxx
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is the obvious way to put $08 into a memory location.
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Not copyrightable.
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$2F -> CPU data direction port
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LDA #$2F
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STA $00
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This is the obvious way to put the recommended default value
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into the 6510's data direction register. Not copyrightable.
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Store $3F somewhere
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LDA #$3F
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STA $xxxx
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Obvious way to achieve this, so not copyrightable.
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Put $7F -> $xx0D
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LDA #$7f
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STA $xx0d
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This is the obvious way to put $7F into a memory location ending in $0D.
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Not copyrightable.
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LDA $DD00 instruction
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Single instructions are not copyrightable
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LDA $DC0D instruction
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Single instructions are not copyrightable.
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Compare A with zero before branching
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CMP #$00
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Bxx $nnnn
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This is a common way to take a branch based on whether the A register
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holds zero or not.
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Take branch based on whether A = $03
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CMP #$03
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Bxx $nnnn
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Common instruction sequence and obvious way to
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take a branch based on whether A = $03.
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Not copyrightable.
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Branch over JMP
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Bxx +
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JMP $xxxx
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*
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Very common sequence to conditionally jump somewhere.
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Not coppyrightable.
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Branch backwards or return
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Bxx *-10
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RTS
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This is the obvious way to either branch backwards or return from a routine.
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i.e. it is a typical loop construct. Not copyrightable.
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Branch over two instructions, first being LDA #$xx
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This corresponds to the following sequence:
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Bxx +
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LDA #$xx
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(two more bytes not matched
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*
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This is the obvious way to conditionally execute two instructions,
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the first of which is LDA #$xx, which is very common.
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That the argument of LDA #$xx doesn't match, nor does the following
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two bytes, adds strength to the argument that this is a non-copyrightable
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sequence of bytes.
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