| ??? 04/29/08 10:52 Read: times |
#154174 - That's just the way it is! Responding to: ???'s previous message |
They are Undefined; Dai Xing said:
but what i want is to know why is that ? Because the chip designers couldn't think of exactly 128 useful SFRs to precisely fill each and every of the available addresses! You should just think of them as unused addresses - reserved for future expansion. Note that newer chips may well have additional SFRs that do, indeed, make use of (some of) these addresses. In fact, some modern chips can't fit all their SFRs into just 128 addresses...! Are those unassigned address is just virtual ? doesn't physically exist? All you need to know is that they are Undefined; that is, these things are not defined - the chip manufacturers are entirely free to do whatever they think best with them, and under no obligation to tell us about it! Therefore, just leave them well alone! |
| Topic | Author | Date |
| problem with unassigned SFR address | 01/01/70 00:00 | |
| Undefined | 01/01/70 00:00 | |
| appreciated! | 01/01/70 00:00 | |
| That's just the way it is! | 01/01/70 00:00 | |
| the one thing is that .... | 01/01/70 00:00 | |
Unassigned SFR addresses | 01/01/70 00:00 |