Re: Branch Instruction Summary
Sean Conner via Coco <coco-uNHYcr1XS/wmlAP/[email protected]>
| Newsgroups | gmane.comp.hardware.tandy.coco |
|---|---|
| Message-ID | <[email protected]> |
It was thus said that the Great Allen Huffman via Coco once stated: > On Jul 22, 2025, at 1:16 PM, John Mark Mobley via Coco <[email protected]> wrote: > > > > All, > > > > See attached. I hope the attachment works. > > I feel this would be very useful to me, with a bit more explaining. I have > never really visualized how some of these other OP codes work with setting > carry or Z or whatever. I know this is all embedded in the OP code > references and such, and maybe I would understand it today, but I sure > didn’t back in 1984. Here's the chart I found. Plain text, and it (to me) explains when to use what branches: +-----------------------------------------------------------------------+ | 6809 BRANCH INSTRUCTIONS | +-------------+-----------------------------+---------------------------+ | Instruction | Description | Condition Formula | +-------------+-----------------------------+---------------------------+ | BCC/BHS | Higher Or Same | XC | | BCS/BLO | Lower | C | | BHI | Higher | XC*XZ | | BLS | Lower Or Same | C + Z | | BNE | Not Equal | XZ | | BEQ | Equal | Z | | BGE | Greater Or Equal (Signed) | N*V + XN*XV | | BLT | Less Than (Signed) | N*XV + XN*V | | BGT | Greater Than (Signed) | N*V*XZ + XN*XV*XZ | | BLE | Less Than Or Equal (Signed) | Z + N*XV + XN*V | | BPL | Plus (Positive) | XN | | BMI | Minus (Negative) | N | | BVC | Overflow Clear | XV | | BVS | Overflow Set | V | | BRA | Always | 1 | | BRN | Never | 0 | +-------------+-----------------------------+---------------------------+ The top four branches are unsigned. I don't even look at the condition formula (but it was handy when writing my own emulator---here X means NOT). -spc -- Coco mailing list [email protected] https://pairlist5.pair.net/mailman/listinfo/coco