ASM code. Note that I'm ORing $4016 with $01 to trigger the bug.
Code:
;see line 17811
;bad code
(17785) C06B LDA #$00 A=01,X=FF,Y=01,S=F5,P=35
(17786) C06D STA $2003 A=00,X=FF,Y=01,S=F5,P=37
(17787) C070 LDA $4F A=00,X=FF,Y=01,S=F5,P=37
(17788) C072 AND #$01 A=00,X=FF,Y=01,S=F5,P=37
(17789) C074 ORA #$02 A=00,X=FF,Y=01,S=F5,P=37
(17790) C076 STA $4014 A=02,X=FF,Y=01,S=F5,P=35
(17791) C079 LDY #$01 A=02,X=FF,Y=01,S=F5,P=35
(17792) C07B STY $4016 A=02,X=FF,Y=01,S=F5,P=35
(17793) C07E DEY A=02,X=FF,Y=01,S=F5,P=35
(17794) C07F STY $4016 A=02,X=FF,Y=00,S=F5,P=37
(17795) C082 LDA $4016 A=02,X=FF,Y=00,S=F5,P=37
(17796) C085 AND #$03 A=01,X=FF,Y=00,S=F5,P=35
(17797) C087 STA $6D A=01,X=FF,Y=00,S=F5,P=35
(17798) C089 LDA $4016 A=01,X=FF,Y=00,S=F5,P=35
(17799) C08C AND #$03 A=01,X=FF,Y=00,S=F5,P=35
(17800) C08E STA $6E A=01,X=FF,Y=00,S=F5,P=35
(17801) C090 LDA $4016 A=01,X=FF,Y=00,S=F5,P=35
(17802) C093 AND #$03 A=01,X=FF,Y=00,S=F5,P=35
(17803) C095 STA $6B A=01,X=FF,Y=00,S=F5,P=35
(17804) C097 LDA $4016 A=01,X=FF,Y=00,S=F5,P=35
(17805) C09A AND #$03 A=01,X=FF,Y=00,S=F5,P=35
(17806) C09C STA $6C A=01,X=FF,Y=00,S=F5,P=35
(17807) C09E LDY #$01 A=01,X=FF,Y=00,S=F5,P=35
(17808) C0A0 LDA $4016 A=01,X=FF,Y=01,S=F5,P=35
(17809) C0A3 AND #$03 A=01,X=FF,Y=01,S=F5,P=35
(17810) C0A5 BNE #$03 A=01,X=FF,Y=01,S=F5,P=35
(17811) C0AA STY $6F A=01,X=FF,Y=01,S=F5,P=35
(17812) C0AC LDY #$01 A=01,X=FF,Y=01,S=F5,P=35
Code:
;good code
(17785) C06B LDA #$00 A=01,X=FF,Y=01,S=F5,P=35
(17786) C06D STA $2003 A=00,X=FF,Y=01,S=F5,P=37
(17787) C070 LDA $4F A=00,X=FF,Y=01,S=F5,P=37
(17788) C072 AND #$01 A=00,X=FF,Y=01,S=F5,P=37
(17789) C074 ORA #$02 A=00,X=FF,Y=01,S=F5,P=37
(17790) C076 STA $4014 A=02,X=FF,Y=01,S=F5,P=35
(17791) C079 LDY #$01 A=02,X=FF,Y=01,S=F5,P=35
(17792) C07B STY $4016 A=02,X=FF,Y=01,S=F5,P=35
(17793) C07E DEY A=02,X=FF,Y=01,S=F5,P=35
(17794) C07F STY $4016 A=02,X=FF,Y=00,S=F5,P=37
(17795) C082 LDA $4016 A=02,X=FF,Y=00,S=F5,P=37
(17796) C085 AND #$03 A=00,X=FF,Y=00,S=F5,P=37
(17797) C087 STA $6D A=00,X=FF,Y=00,S=F5,P=37
(17798) C089 LDA $4016 A=00,X=FF,Y=00,S=F5,P=37
(17799) C08C AND #$03 A=00,X=FF,Y=00,S=F5,P=37
(17800) C08E STA $6E A=00,X=FF,Y=00,S=F5,P=37
(17801) C090 LDA $4016 A=00,X=FF,Y=00,S=F5,P=37
(17802) C093 AND #$03 A=00,X=FF,Y=00,S=F5,P=37
(17803) C095 STA $6B A=00,X=FF,Y=00,S=F5,P=37
(17804) C097 LDA $4016 A=00,X=FF,Y=00,S=F5,P=37
(17805) C09A AND #$03 A=00,X=FF,Y=00,S=F5,P=37
(17806) C09C STA $6C A=00,X=FF,Y=00,S=F5,P=37
(17807) C09E LDY #$01 A=00,X=FF,Y=00,S=F5,P=37
(17808) C0A0 LDA $4016 A=00,X=FF,Y=01,S=F5,P=35
(17809) C0A3 AND #$03 A=00,X=FF,Y=01,S=F5,P=37
(17810) C0A5 BNE #$03 A=00,X=FF,Y=01,S=F5,P=37
(17811) C0A7 DEY A=00,X=FF,Y=01,S=F5,P=37
(17812) C0A8 BPL #$F6 A=00,X=FF,Y=00,S=F5,P=37
(17813) C0A0 LDA $4016 A=00,X=FF,Y=00,S=F5,P=37