| ??? 02/16/06 02:45 Read: times |
#110117 - Main origin of problems Responding to: ???'s previous message |
Trevor said:
After reducing the value of the 100 Ohm resistors to 25 Ohms (except for the reset line) that go to the processor (not the LPT port resistors) it works great for the 8252 as well. I think the main reason for problems is that most printer ports emit TTL-signals, which is a problem for the 74VHC244. Then, the least mismatch of cable termination will cause transmission errors. Today I think that this 74VHC244 is not a state-of-the-art solution. Better is what I recommended here: http://www.8052.com/forum/read.phtml?id=103574 Trevor said:
After switching to EPP the signal was nice and square. This is a good hint! Indeed, signals of printer port often show rounded knees with horrible rise times... Kai |
| Topic | Author | Date |
| Atmel AT89 ISP Problems Solved... | 01/01/70 00:00 | |
Main origin of problems | 01/01/70 00:00 |