| ??? 12/22/04 04:49 Read: times |
#83606 - Circuit Explained Responding to: ???'s previous message |
OK, real easy circuit, in a nutshell, the 74HC14's are schmitt triggers, not just inverters. A combination of these and the 1000pF caps correct for rounding off of the parallel ports square waves through a parallel port cable. This corrects some timing issues that I was having initially.
Second, the 74HC126 disconnects the programmer from the parallel port when programming is not active. BTW you can change this chip to a 74HC125 and the circuit works with AVR chips except for the reset button, you'd need to tie that to GND as the AVR's use a low reset vs. the high reset of MCS51 devices. Hope this helps... 73 - Trev - K6ESE |
| Topic | Author | Date |
| at89 programmer | 01/01/70 00:00 | |
| Link non-functional | 01/01/70 00:00 | |
| RE: Link non-functional | 01/01/70 00:00 | |
| Possible suggestion | 01/01/70 00:00 | |
| RE: Possible suggestion | 01/01/70 00:00 | |
| RE: Possible suggestion | 01/01/70 00:00 | |
| Try this | 01/01/70 00:00 | |
| RE: Try this | 01/01/70 00:00 | |
| RE: Try this | 01/01/70 00:00 | |
| Now what does it look like? | 01/01/70 00:00 | |
| RE: Now what does it look like? | 01/01/70 00:00 | |
| Some more ideas | 01/01/70 00:00 | |
| RE: Some more ideas | 01/01/70 00:00 | |
| RE: Some more ideas | 01/01/70 00:00 | |
Circuit Explained | 01/01/70 00:00 | |
| New K6ESE Web Page - Uploader | 01/01/70 00:00 | |
| RE: at89 programmer | 01/01/70 00:00 | |
| RE: at89 programmer | 01/01/70 00:00 | |
| gotcha | 01/01/70 00:00 | |
| RE: gotcha | 01/01/70 00:00 | |
| RE: gotcha | 01/01/70 00:00 | |
| RE: gotcha | 01/01/70 00:00 | |
| RE: gotcha | 01/01/70 00:00 | |
| Why burden capacitors are needed... | 01/01/70 00:00 | |
| Must be a part of site FAQ | 01/01/70 00:00 | |
| RE: Must be a part of site FAQ | 01/01/70 00:00 | |
| RE: Must be a part of site FAQ | 01/01/70 00:00 |