| ??? 11/06/05 12:39 Read: times |
#103334 - VHC-version is needed Responding to: ???'s previous message |
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! So, this VHC-type is actually needed! You can buy it from Digikey (look under Toshiba). Another cause of problems can be the ribbon cable. Have a look at the special application note from atmel, discussing this ribbon cable: http://www.atmel.com/dyn/resou...oc3310.pdf Use a flat ribbon cable showing exactly the same pinning! also i dont't understand how the error circuit works in this schematic It's quite simple: The three diodes provide a "constant" reference voltage at the one input of comparator. The other input gets a fraction of Vcc. If Vcc is proper the ouptut of comparator is logic high, otherwise it's logic low. Kai |
| 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 |