Timeline for about flag changes in 16-bit calculations on the MC6800
Current License: CC BY-SA 4.0
14 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Aug 30 at 3:18 | vote | accept | zu2 | ||
| Aug 29 at 6:31 | comment | added | Simon Richter | To clarify that I've understood the problem correctly: comparing 0 and 1 would give the same flags as comparing 1 and 0, because there is no carry from the bottom byte to the top byte, both top bytes are zero, so N and V are unset in either case? | |
| Aug 28 at 13:57 | vote | accept | zu2 | ||
| Aug 28 at 13:58 | |||||
| Aug 28 at 12:38 | history | became hot network question | |||
| Aug 28 at 9:36 | answer | added | Justme | timeline score: 6 | |
| Aug 28 at 7:57 | answer | added | the busybee | timeline score: 10 | |
| Aug 28 at 7:41 | comment | added | the busybee | Please edit your question to add new information, I have done this for you now. You might also want to add the URLs of the mentioned manuals. | |
| Aug 28 at 7:40 | history | edited | the busybee | CC BY-SA 4.0 |
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| Aug 28 at 7:30 | answer | added | lvd | timeline score: 4 | |
| Aug 28 at 6:04 | comment | added | zu2 | I am looking at M6800 Microprocessor Applications Manual (1975). p.1-19. I also looked at Hitachi's manual, but there is no big difference. In this manual, the N flag change of the CPX instruction is written as follows. "(Bit N) Test: Sign bit of most significant (MS) byte of result = I?" I think it is difficult to understand this is an 8-bit comparison. Of course, this description is different from LDX/STX, so we can guess that something strange is going on. "(Bit N)Test: Result less than zero? (Bit 15 = 1)" I would like a document that clearly explains these differences. | |
| Aug 28 at 5:55 | comment | added | the busybee | Welcome to SE/Retrocomputing! Please take the tour to learn how this site works, and read "How to Ask". Then come back and edit your question to clarify. What 6800 manual are you using to find out? And why does it not help you? | |
| Aug 28 at 5:26 | comment | added | Justme | What exact opcodes are you talking about, and why would not the CPU programming manual offer a correct description how each instruction works? | |
| S Aug 28 at 4:38 | review | First questions | |||
| Aug 28 at 8:00 | |||||
| S Aug 28 at 4:38 | history | asked | zu2 | CC BY-SA 4.0 |