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z80a: add ELSE,
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@ -300,11 +300,10 @@ CREATE lblnext 0 , ( stable ABI until set in B300 )
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: IFC, JRNC, FJR, ;
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: IFC, JRNC, FJR, ;
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: IFNC, JRC, FJR, ;
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: IFNC, JRC, FJR, ;
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: THEN,
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: THEN,
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DUP PC ( l l pc )
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DUP PC ( l l pc ) -^ 1- ( l off )
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-^ 1- ( l off )
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( warning: l is a PC offset, not a mem addr! )
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( warning: l is a PC offset, not a mem addr! )
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SWAP ORG @ + BIN( @ - ( off addr )
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SWAP ORG @ + BIN( @ - ( off addr ) C! ;
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C! ;
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: ELSE, JR, FJR, SWAP THEN, ;
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( ----- 027 )
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( ----- 027 )
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: FWR BSET 0 C, ;
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: FWR BSET 0 C, ;
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: FSET @ THEN, ;
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: FSET @ THEN, ;
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@ -87,6 +87,11 @@ the opposite condition is met, a relative jump is made to
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THEN,'s PC. For example, if you have IFZ, a jump is made when
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THEN,'s PC. For example, if you have IFZ, a jump is made when
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Z is unset.
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Z is unset.
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There can be an ELSE, in the middle of an IF, and THEN,. When
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present, IF, jumps to it when the condition is unmet. When the
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condition is met, upon reaching the ELSE, we unconditionally
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jump to the THEN,.
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On the BEGIN,..AGAIN, side, it's a bit different. You start
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On the BEGIN,..AGAIN, side, it's a bit different. You start
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with your BEGIN, instruction, and then later you issue a
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with your BEGIN, instruction, and then later you issue a
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JRxx, instr followed by AGAIN,. Exactly like you would do
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JRxx, instr followed by AGAIN,. Exactly like you would do
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@ -96,7 +101,7 @@ On top of that, you have the very nice BREAK, instruction,
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which must also be preceded by a JRxx, and will jump to the
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which must also be preceded by a JRxx, and will jump to the
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PC following the next AGAIN,. Examples:
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PC following the next AGAIN,. Examples:
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IFZ, NOP, THEN,
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IFZ, NOP, ELSE, NOP, THEN,
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BEGIN, NOP, JR, AGAIN, ( unconditional )
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BEGIN, NOP, JR, AGAIN, ( unconditional )
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BEGIN, NOP, JRZ, AGAIN, ( conditional )
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BEGIN, NOP, JRZ, AGAIN, ( conditional )
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BEGIN, NOP, JRZ, BREAK, JR, AGAIN, ( break off the loop )
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BEGIN, NOP, JRZ, BREAK, JR, AGAIN, ( break off the loop )
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