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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"MCL6809 project: bug in ANDCC and ORCC instructions","articleBody":"Hi Ted,\n\nNice projects. I was using the MCL6809.ino and found a problem in the instructions opcode_0x1C () and opcode_0x1CA() for the respective instructions ANDCC immediate and ORCC immediate.\n\nReplace `UpdateFlags( AND_Common(REGISTER_CC,ea_data8) );` , with `UpdateFlags(REGISTER_CC \u0026 ea_data8) ;`\nand replace `UpdateFlags( OR_Common(REGISTER_CC,ea_data8) );` , with `UpdateFlags(REGISTER_CC | ea_data8) ;` to solve it.\n\nThe reason is that the AND_Common and OR_Common subroutines will change the NZV flags after the operation.\nIn some cases this may give the wrong result.\nFor instance V flag will be cleared, irrespective of the value of the operands.\nIf all the flags were all cleared before the ANDCC instruction, the zero flag will be set. That should not happen either.\n\nCheers.","author":{"url":"https://github.com/Pieter56","@type":"Person","name":"Pieter56"},"datePublished":"2026-02-02T11:05:14.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":1},"url":"https://github.com/51/Projects/issues/51"}