| ??? 02/16/05 01:14 Read: times |
#87599 - Ouch! Responding to: ???'s previous message |
Ray said:
I have built the above circuit (wirewrapped) and I have a 0.1uF decoupling cap connected to the VCC pin of the 8051. Using the following code sometimes the LED stays on, other times it goes off, but it never keeps flashing. And in your schematic the use of a FAST-TTL chip can be seen! FAST-TTL and wirewrapped design is a dangerous combination. Try to avoid fast digital chips, unless you have a proper printed circuit board design using a solid ground plane. And, not only the micro needs power supply decoupling capacitor, but also the 74F14. Try the much slowlier 74HC14. And look for a good ground signal routing providing low inductivity. Last word, which shall not at all offend you: Drawing a schematic makes only sense, if every connection is shown. This includes /EA/Vpp pin, Vcc and ground pins and power supply decoupling capacitors. Kai |
| Topic | Author | Date |
| Problem getting 8051 chip to work | 01/01/70 00:00 | |
| tie ~EA pin to Vcc | 01/01/70 00:00 | |
| tie Vpp/~EA pin to Vcc | 01/01/70 00:00 | |
| to connect or not? | 01/01/70 00:00 | |
| conbnect | 01/01/70 00:00 | |
| If it helps.... | 01/01/70 00:00 | |
| Reset Capacitor | 01/01/70 00:00 | |
| connect | 01/01/70 00:00 | |
| T89C51RD2 | 01/01/70 00:00 | |
| This device is ISP | 01/01/70 00:00 | |
| VCC and GND? | 01/01/70 00:00 | |
| I think you do not load | 01/01/70 00:00 | |
| Series resistor for LED? | 01/01/70 00:00 | |
| 74F14 | 01/01/70 00:00 | |
| give me +1 too | 01/01/70 00:00 | |
| done | 01/01/70 00:00 | |
| Sorry | 01/01/70 00:00 | |
| LED Polarity | 01/01/70 00:00 | |
| Does not seem to be the cause | 01/01/70 00:00 | |
| Ouch! | 01/01/70 00:00 | |
| FAST-TTL and breadboarded design | 01/01/70 00:00 | |
| Ground bounce | 01/01/70 00:00 | |
| Bad news 74F =( | 01/01/70 00:00 | |
| HCT? | 01/01/70 00:00 | |
| LS, HCT and maybe AHCT | 01/01/70 00:00 | |
| Got it | 01/01/70 00:00 | |
| wire wrap and breadboards | 01/01/70 00:00 | |
| I use protoboard | 01/01/70 00:00 | |
| the problem with that is | 01/01/70 00:00 | |
| Thanks | 01/01/70 00:00 | |
| Why do you want to use 74F chips? | 01/01/70 00:00 | |
well... | 01/01/70 00:00 | |
| maybe you are still in ISP mode? | 01/01/70 00:00 | |
| 1st things 1st please | 01/01/70 00:00 | |
| Thanks | 01/01/70 00:00 | |
| bounce on non PCB | 01/01/70 00:00 | |
| Analytical thinking | 01/01/70 00:00 |