| ??? 01/17/13 19:59 Read: times |
#189229 - Clarifies Responding to: ???'s previous message |
Koen De Ganck said:
So, for future designs of upgrades, it could be a good idea to place a pull up. I think only if you have external (pull down?) loads on PSEN ? A PSEN normally not connected, will not be pulled low. I measured -27uA on a gnded pin, and -225uA on ~1.85V, so it is a QuasiIO pin, during RST active. After reset exit, it has a strong pullup (-18mA) Boot mode is entered if PSEN is seen to be low on RST de-assert. Koen De Ganck said:
I updated about 20 boards with a pull-up of 560K on pin 'PSEN'.
All but 1 board started up in a good way (10-20 tries), although most of them failed many times without pull-up. The single board that had 1 failure out of 20, worked well with a pull-up of 330K. While is it nice to know the boundary condition, I would fit well under 330K to allow for temperature and device margins. Koen De Ganck said:
PSEN : is loaded with 1 port, the traces are within 2 x 3cm (4 endpoints ) on a multilayer. What exactly is this load ? Koen De Ganck said:
I also remove the LM810 reset chip as this is not needed anymore as the board works on 3V3. I thought something else was driven by RST ? I know a SW reset will drive out on RST pin, but I'm not sure if Power-Up does ? |
| Topic | Author | Date |
| Reset issue with new Atmel AT89LP51ED2 | 01/01/70 00:00 | |
| Do never use a µC from which only a preliminary... | 01/01/70 00:00 | |
| configuration settings | 01/01/70 00:00 | |
| what about negative reset? | 01/01/70 00:00 | |
| good idea but | 01/01/70 00:00 | |
| Some things to check... | 01/01/70 00:00 | |
| also try no LM810 at all | 01/01/70 00:00 | |
| reset is inverted | 01/01/70 00:00 | |
| no strange signals | 01/01/70 00:00 | |
| Extra modes ? | 01/01/70 00:00 | |
| pull-up on PSEN solves the problem | 01/01/70 00:00 | |
| small capacitor ? | 01/01/70 00:00 | |
| small capacitor | 01/01/70 00:00 | |
| side-stepping the problem? | 01/01/70 00:00 | |
| SST could be an option | 01/01/70 00:00 | |
| final status AT89LP51ED2 reset | 01/01/70 00:00 | |
| Clarifies | 01/01/70 00:00 | |
| loads on PSEN | 01/01/70 00:00 | |
| An isolated PSEN works fine ? | 01/01/70 00:00 | |
| GAL causes problem | 01/01/70 00:00 | |
| ATF16V8CZ has Pin-keeper | 01/01/70 00:00 | |
| 'Z' indeed | 01/01/70 00:00 | |
| ATF16V8BQL has Icc of ~1.5mA | 01/01/70 00:00 | |
'BQL' version could be an option | 01/01/70 00:00 |