| ??? 04/02/07 21:52 Read: times |
#136449 - MOVC question |
When executing a MOVC instruction from external program memory (/EA tied to ground), will it return data from the external program memory or the internal, on-chip memory?
Older 8751 datasheets seem to indicate a security bit was added strictly for the purpose of preventing a MOVC instruction located in external program memory from reading internal memory. So I would suspect this is the case. On the other hand that would seem to make MOVC much less useful - this could be why many applications use mixed external code/data so MOVX can be used to access data. If it does access internal program memory, is /PSEN asserted during the read? Normally when executing internal code /PSEN is always high so you can't monitor execution, so I'm thinking it would be disabled. |
| Topic | Author | Date |
| MOVC question | 01/01/70 00:00 | |
| what derivative? | 01/01/70 00:00 | |
| Re: MOVC question | 01/01/70 00:00 | |
| MOVC is external with /EA low | 01/01/70 00:00 | |
| Eureka! | 01/01/70 00:00 | |
| You are correct | 01/01/70 00:00 | |
| Derivative dependent | 01/01/70 00:00 | |
| I'm a classical sort of guy | 01/01/70 00:00 | |
| I think it is irrelevant to discuss derivatives... | 01/01/70 00:00 | |
| not discussing such | 01/01/70 00:00 | |
| for example DS89C4x0? | 01/01/70 00:00 | |
| yup | 01/01/70 00:00 | |
| Blast from the past | 01/01/70 00:00 | |
| this is how it works with an unlocked AT89C52 | 01/01/70 00:00 | |
| Nice work | 01/01/70 00:00 | |
miniLA | 01/01/70 00:00 | |
| an answer | 01/01/70 00:00 |