Data commit

Task/Gotchas/68000-Assembly/gotchas-1.68000

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+MOVE.L $12345678,D0  ;move the 32-bit value stored at memory address $12345678 into D0
+MOVE.L #$12345678,D0 ;load the D0 register with the constant value $12345678

Task/Gotchas/68000-Assembly/gotchas-2.68000

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+DC.B $45  ;this is the literal constant value $45, not "the value stored at memory address 0x0045"

Task/Gotchas/68000-Assembly/gotchas-3.68000

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+MOVEA.L #$A04000,A0  ;load the address $A04000 into A0
+MOVE.L A0,D0         ;move the quantity $A04000 into D0
+MOVE.B (A0),D0       ;get the 8-bit value stored at memory address $A04000, and store it into the lowest byte of D0.
+MOVE.W (4,A0),D1     ;get the 16-bit value stored at memory address $A04004, and store it into the low word of D1.

Task/Gotchas/68000-Assembly/gotchas-4.68000

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+LEA $A04000,A0  ;effectively MOVEA.L #$A04000,A0
+LEA (4,A0),A0   ;effectively ADDA.L #4,A0

Task/Gotchas/68000-Assembly/gotchas-5.68000

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+MOVE.L #$12345678,D0 ;set the entire register to a known value for demonstration purposes.
+
+MOVE.W #$7FFF,D0 ;D0 = $12347FFF
+ADD.W #1,D0      ;D0 = $12348000
+TRAPV ;the above operation set the overflow flag, so this instruction will call the signed overflow handler.
+;Even though the entire register didn't overflow, the portion we were operating on did, so that counts.

Task/Gotchas/68000-Assembly/gotchas-6.68000

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+MOVE.B #16-1,D0 ;loop 16 times
+forloop:
+; loop body goes here
+DBRA D0,forloop

Task/Gotchas/68000-Assembly/gotchas-7.68000

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+MOVEA.W #$8000,A0 ;MOVEA.L #$FF8000,A0
+MOVEA.W #$7FFF,A0 ;MOVEA.L #$007FFF,A0

Task/Gotchas/68000-Assembly/gotchas-8.68000

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+MOVE.W #$FF,D0   ;MOVE.W #$00FF,D0
+MOVE.L #$8000,D2 ;MOVE.L #$00008000,D2

Task/Gotchas/68000-Assembly/gotchas-9.68000

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+MOVE.W #$FF,D0
+EXT.W D0 ;D0 = $????FFFF
+
+MOVE.L #$8000,D1
+EXT.L D1 ;D1 = $FFFF8000