| ??? 11/07/05 08:38 Read: times |
#103352 - absolutely necessary? Responding to: ???'s previous message |
Kai Klaas said:
Ant said:
but i am using a 74hc244 instead of a 74vhc244 which i can't get working. The VHC-version is necessary, because it does not contain internal protection diodes from each input to Vcc. This allows you to power the 74VHC244 by the target's Vcc, without causing trouble when the target's Vcc is off and having the programmer connected to the printer port! Please correct me if I am wrong, but I understood it that if I always forst connect the target, power it on and then connect the PC's parallel port, the HC's will do, won't they? Also, I somehow can't believe they will do any damage to the PC's parallel port, except it won't detect the target-power-off state... Am I wrong? On the other hand, I am not in favour of the parallel-port-connected "cables", buffered or not, (including - or because of - the popular CPLD "downloading" "cables"). I'd prefer either a serial port connected cable (such as the Ulrich Bangert's - pity his site is off-line, but I have stored the stuff somewhere) or better an "intelligent" solution with a proper serial-to-SPI "bridge" (Peter Dannegger has a solution for AT89S53 on his website - maybe we could persuade him to upgrade it also for AT89S52... :-) ) Jan Waclawek |
| Topic | Author | Date |
| atmel isp | 01/01/70 00:00 | |
| check out | 01/01/70 00:00 | |
| isp | 01/01/70 00:00 | |
| home Atmel ISP cable | 01/01/70 00:00 | |
You could try this... | 01/01/70 00:00 | |
| VHC-version is needed | 01/01/70 00:00 | |
| absolutely necessary? | 01/01/70 00:00 | |
| If it was so simple... | 01/01/70 00:00 | |
| 74vhc244 | 01/01/70 00:00 | |
| No access to digikey in Australia? | 01/01/70 00:00 | |
| can somebody please explain | 01/01/70 00:00 | |
| Here comes my explaination | 01/01/70 00:00 | |
| bad nomenclature ... | 01/01/70 00:00 | |
| Nomenclatura | 01/01/70 00:00 | |
| just explaination | 01/01/70 00:00 |