| ??? 09/02/06 12:07 Modified: 09/02/06 12:10 Read: times |
#123574 - You are missing... Responding to: ???'s previous message |
Sender Jones said:
If 128 ram overlay on SFR, and instructions such as call, push etc will write to stack, then it will still overwrite some of the SFR that is after 85h (e.g. PCON in 87h, TCON in 88h)though it is indirectly. I must have missed out something here. Please help again. Perhaps a diagram would help? Take a look at Fig 6 on p3 of the 80C51 Architecture document (Chapter 1 of the so-called "bible" for the 8051): http://www.nxp.com/acrobat_d...ARCH_1.pdf You can see that the upper 128 bytes of RAM are accessible by indirect addressing only - that's why indirect addressing doesn't affect the SFRs and, conversely, why SFRs can't be indirectly addressed! The new addresses for the other "bible" chapters are: Chapter 1 - 80C51 Family Architecture: http://www.nxp.com/acrobat_d...ARCH_1.pdf Chapter 2 - 80C51 Family Programmer’s Guide and Instruction Set: http://www.nxp.com/acrobat_d...UIDE_1.pdf Chapter 3 - 80C51 Family Hardware Description: http://www.nxp.com/acrobat_d...WARE_1.pdf See: http://www.8052.com/forumchat/read.phtml?id=123508 |
| Topic | Author | Date |
| Newbie need help | 01/01/70 00:00 | |
| 8052 Magic | 01/01/70 00:00 | |
| stack overlay on SFR | 01/01/70 00:00 | |
| You are missing... | 01/01/70 00:00 | |
| Same address, different circuits | 01/01/70 00:00 | |
| Confused?! | 01/01/70 00:00 | |
| peculiarities | 01/01/70 00:00 | |
| link | 01/01/70 00:00 | |
| Thanks. | 01/01/70 00:00 | |
| 8051 vs 8052 | 01/01/70 00:00 | |
understatement of the year | 01/01/70 00:00 |