??? 04/21/11 03:41 Read: times |
#181959 - Timing Responding to: ???'s previous message |
A good reset circuit is needed to make sure the processor gets properly reset if VCC rises slowly or fast, or if there is glitches on VCC or if you turn off power for a very short time. The problem with RC solutions is that they can work perfectly for first-time power-on when the capacitor started out completely empty, but have huge problems with restarting the processor if you quickly disconnect/reconnect power. Note that contact bounce when turning on the power can result in failures with RC reset solutions because the first bounce may manage to charge the cap while the processor locks up during the short absence of power but don't get a second reset on the next bounce.
A real reset circuit should use active components, meaning that they can respond quickly in all conditions. Anyway - I don't know what you mean with "commands" in your post. But if the processor boots but then runs differently far before hanging, then you probably have other problems. You might have marginal supply voltages. Or marginal timing on some critical signals (very important when using external memory). Or maybe the oscillator is running at wrong speed. Or maybe the oscillator isn't running stable. Do you have proper decoupling on the supply voltages? Is your ground plane stable? |
Topic | Author | Date |
Is 80C535 Compatible with 80C31? | 01/01/70 00:00 | |
do not use pin numbers | 01/01/70 00:00 | |
Supervisor Chip | 01/01/70 00:00 | |
you say you want to test chips | 01/01/70 00:00 | |
Reset Circuitry for 80C535 | 01/01/70 00:00 | |
Timing | 01/01/70 00:00 | |
probably because ... | 01/01/70 00:00 | |
Supervisor/Watchdog Timer chip | 01/01/70 00:00 | |
No timer needed to kick watchdog | 01/01/70 00:00 | |
The internal Watchdog Timer | 01/01/70 00:00 | |
good choice | 01/01/70 00:00 | |
NE555 | 01/01/70 00:00 | |
8051 and 555 reset | 01/01/70 00:00 | |
555 Reset circuitry | 01/01/70 00:00 | |
bad choice | 01/01/70 00:00 | |
Reset Supervisor | 01/01/70 00:00 | |
there are other possibilities | 01/01/70 00:00 | |
Other source | 01/01/70 00:00 | |
did the datasheet not say so? | 01/01/70 00:00 | |
It says so | 01/01/70 00:00 | |
would it not be a good idea to do so before ... | 01/01/70 00:00 | |
explain a bit about the nessecity of Supervisor Chip | 01/01/70 00:00 |