| ??? 03/10/07 23:17 Read: times |
#134691 - be more specific Responding to: ???'s previous message |
Mike Stegmaier said:
I have assembled my board, and some components appear to work well.
Basically, I took on someones idea of loading the chip directly with data instead of making a "hardware ROM". I actually used the idea and did it straight to the EEPROM. OK, so you made an EEPROM programmer with your PC's parallel port Now according to my tests, (Yes, I'm the wise one that uses an LED and resistor in series to test several connection points. It is faster than a multimeter)... Now, my hardware tests show that I am able to send any data from the PC (computer) to any of the first 256 bytes of EEPROM space. Yes, I checked the logic on it. I have no doubts about you being able to send your data to the EEPROM. Can you verify the codes programmed? Are they correct? You did not mention your EEPROM verified correctly. HOWEVER, as soon as I tried running the code off of the EEPROM (even with the parallel port disconnected from the circuit (using a 74HC245) I get erratic results. Define erratic... Does it sometimes work? and sometimes not? Or do you get only a part of it that's working? for some reason, it partially works. Again, be more specific, what works and what does not? What do you observe? Suppose you went to a garage with your car and you said: "It partially works"... what would the technician know? But if you said: "If that indicator needle is the red zone, and that yellow sign is lit, it stalls and won't start again", you'd probably be told that you then need to get some fuel... Much of my decoding logic has been taken from PJRC's design. See the following URL: http://pjrc.com/tech/8051/board5/schematic.html My 4-input nand gates and decoder are connected in the same way, and my LCD enable is connected to a NOR gate output. The NOR inputs are connected to the processor WR pin and Y0 (address 0) of the decoder (74HC138). My nand gates are 74HC20, while the published one is 74AC20. I was just wondering, do I need tons of resistors? I ask that because when the program runs off of the ROM, I want the WR pin to be high. Likewise, I want the RD pin to be high when I am programming the rom. Also, all of the chips I use are of the same family (74HC). regards Patrick |
| 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 |