| ??? 08/19/06 04:12 Modified: 08/19/06 04:12 Read: times |
#122615 - Bus contention is hardly to happen, unless... Responding to: ???'s previous message |
Richard said:
If power-down was not intended to allow corruption of external RAM, I'd suggest that it's very important to ensure that nRD and nWR are never active during idle or power-down. Once that's done, it shouldn't matter at all what happens on nPSEN or ALE. As Port3 emits content of according SFR, and logic high has once to be written into SFR of P3.7, to be able to address external RAM, read line will automatically emit logic high on power-down. So, external code memory and RAM will not drive the data bus at the same time. No bus contention will occur. But you are right: If SFR of P3.7 is changed to logic low before a power down, by a (heavily unsuited!) instruction of code, while having external RAM and code memory connected to the micro, trouble will occur... Kai |
| Topic | Author | Date |
| Status of ALE and PSEN in IDLE and PD mode | 01/01/70 00:00 | |
| YES! | 01/01/70 00:00 | |
| WHAT??? You're kidding, right? | 01/01/70 00:00 | |
Bus contention is hardly to happen, unless... | 01/01/70 00:00 |