| ??? 03/11/07 00:46 Modified: 03/11/07 01:53 Read: times |
#134694 - interesting tests Responding to: ???'s previous message |
I think I have to add more resistors.
I had it under one configuration (I can't remember it now, since I adjusted the resistor positions so much), where in the programming stage, the code was actually running, yet the RD pin was only tied to the microprocessor and the microprocessor was in reset. At the programming stage, a set of 74HC125 buffers are enabled. one buffer output is tied to ALE, and the input of that buffer is tied to the parallel port. The enable is connected to reset enable. This allows the port to use the address latch. I have another buffer where the input is grounded, and the output is tied to the WR pin of the EEPROM, RAM, and CPU. the enable is connected to the parallel port, so it can also determine when the WR line goes low. I have an 8 bit buffer that allows the data to go through. Its enable pin is also tied to the reset enable. this reset enable is nanded with a push button reset (which defaults to high through a pull-up resistor). When the "reset enable" goes low and/or the push button goes low, the buffers mentioned above are enabled and the CPU is in reset. I think I need resistors on some address lines, the RD, the WR, and the PSEN pins. Please help. Every chip I am using is CMOS compatible. PS: I enclosed a schematic right now. Take a look at: http://www.rootshell.be/~mik3ca/cir.bmp Someone complained about bandwidth so I no longer will post it here. |
| Topic | Author | Date |
| 8051 board somewhat working | 01/01/70 00:00 | |
| Give us a clue then.How does it partialy work?? | 01/01/70 00:00 | |
| HC AC ???? | 01/01/70 00:00 | |
| you will most likely need pullups | 01/01/70 00:00 | |
| pull ups | 01/01/70 00:00 | |
| be more specific | 01/01/70 00:00 | |
| interesting tests | 01/01/70 00:00 | |
| interesting they may be, but | 01/01/70 00:00 | |
| to verify | 01/01/70 00:00 | |
| interesting they may be, | 01/01/70 00:00 | |
| Checksum? CRC? | 01/01/70 00:00 | |
| hmm | 01/01/70 00:00 | |
| You probably need an oscilloscope | 01/01/70 00:00 | |
| sorry for asking | 01/01/70 00:00 | |
| not the first... (or last :-) | 01/01/70 00:00 | |
| Maybe my naging helped ... | 01/01/70 00:00 | |
| why EPP? | 01/01/70 00:00 | |
| why epp can be faster | 01/01/70 00:00 | |
| Epp requires a bit less logic and is WAY faster | 01/01/70 00:00 | |
| about that schematic ... | 01/01/70 00:00 | |
| a matter of taste | 01/01/70 00:00 | |
| I have to agree ... | 01/01/70 00:00 | |
you may not have discovered this | 01/01/70 00:00 | |
| you have to investigate | 01/01/70 00:00 | |
| indeed | 01/01/70 00:00 | |
| Amazed! | 01/01/70 00:00 | |
| What? | 01/01/70 00:00 |