| ??? 09/03/05 17:49 Read: times |
#100549 - 8052.com SBC weird ISP behavior. |
When I try to use VisISP to update the SBCMON to ver 1.3 I have a very difficult time conncting to and reading and writing to the mcu. In trying to determine if signal levels are correct on the parallel connector I found that whenever my scope probe is touching pin 2 of U12 (74HC126) Clock signal, all three operations work, even though on writing to the mcu I consistently get 22 byte and 22 address errors. The monitor program starts up and appears to work fine (once I configured Hypercom to append LF to CR).
Back to pin 2, even touching a wire with which I am in contact results in completed operations. I tried using a 4.7k pullup but that did not help. The cable from the PC to the SBC is a standard pc printer cable where I replaced the Centronics connector with a female DB25, making only the connections listed in the schematics. Any suggestions? |
| Topic | Author | Date |
| 8052.com SBC weird ISP behavior. | 01/01/70 00:00 | |
| ISP | 01/01/70 00:00 | |
| Just pin 2 | 01/01/70 00:00 | |
| scope probe | 01/01/70 00:00 | |
| As you were typing... | 01/01/70 00:00 | |
| Possible fix? | 01/01/70 00:00 | |
| flat? | 01/01/70 00:00 | |
| This one be round | 01/01/70 00:00 | |
| Cap | 01/01/70 00:00 | |
| Cap | 01/01/70 00:00 | |
| ISP and problems | 01/01/70 00:00 | |
| 100pF vs 1000pF | 01/01/70 00:00 | |
Re 100/1000pF | 01/01/70 00:00 |