| ??? 10/06/05 07:48 Read: times |
#102015 - '420 Responding to: ???'s previous message |
Jeff Corr said:
I'm using the Dallas 420 derivative. I built a board last night
which I'm having problems with in that it will not get into the boot loader. I've got an 8Mhz crystal in it. Reason I was asking is because in that table there (from the link you gave me), you can clearly see 8Mhz is supported at several baud rates for the bootloader, but in the Dallas datasheets there is no such table. I would assume these two derivatives are similar. For my higher performance applications, I often use Epson SG-531 series oscillators running at 29.4910 MHz for my DS89C4x0 devices. This gives me excellent matches for a wide range of common PC baud rates. There are several changes I am using over previous circuits. This circuit is designed to be a little "line following" robot, so it will only need to be programmed once. As such, I didn't use the DTR/DSR line from the serial port to trigger the boot loader. I am manually bringing RSET, PSEN and EA to 1,0,0 with jumpers. I will check the board again to see if I left something out or got one little line wrong, but I don't think I did - however, I do think the loader is responding, because when I attempt to connect to it with the MTK, in some baud rates, I get "junk" data back, indicating a response at a different serial rate. Any other thoughts? There's a very good chance of that you're seeing a response at an inappropriate data rate. So, what rate are you trying to connect at with MTK? Is this baud rate one of the rates that the autobaud routine will try? The timer reload values attempted by the loader are specified in the documentation. Also, using my 29.4910 MHz oscillators, anyway, I've never had luck programming a DS89C420 or DS89C450 at speeds higher than 38400 bps. I'm not sure why that is, but when in doubt, a slower speed is worth a try. Secondly, assuming the answer to the first question is yes, given your oscillator, what is the expected deviation from the corresponding PC baud rate? If it's more than a couple percent, problems are very likely. Again, make sure your ISP circuit is correct as you think it is. Finally, you can certainly try my own 89C4x0ldr-lite loader software, but I've never known it to work in situations where MTK won't. --Sasha Jevtic |
| Topic | Author | Date |
| Other crystals? | 01/01/70 00:00 | |
| my experience | 01/01/70 00:00 | |
| dallas | 01/01/70 00:00 | |
| RTFM | 01/01/70 00:00 | |
| the speedy '450 | 01/01/70 00:00 | |
| why 8MHz? | 01/01/70 00:00 | |
| crystals | 01/01/70 00:00 | |
| '420 | 01/01/70 00:00 | |
| errata? | 01/01/70 00:00 | |
| 22.1184MHz | 01/01/70 00:00 | |
| since when? | 01/01/70 00:00 | |
| the tiny asterisk... | 01/01/70 00:00 | |
| Baud rates | 01/01/70 00:00 | |
| crystals, but problem fixed.... sorta :) | 01/01/70 00:00 | |
| 10472 baud | 01/01/70 00:00 | |
| but Atmel | 01/01/70 00:00 | |
| 8 bits autobaud | 01/01/70 00:00 | |
| explanation | 01/01/70 00:00 | |
| dallas | 01/01/70 00:00 | |
| 7.3728MHz | 01/01/70 00:00 | |
| Lower clock frquency | 01/01/70 00:00 | |
| backslashes | 01/01/70 00:00 | |
| New Server Problems? | 01/01/70 00:00 | |
| lol | 01/01/70 00:00 | |
| Go on laughing... | 01/01/70 00:00 | |
| rise/fall time? | 01/01/70 00:00 | |
| that is absolutely correct, but what mak | 01/01/70 00:00 | |
| jetplanes | 01/01/70 00:00 | |
| It's a combination of both | 01/01/70 00:00 | |
| thread | 01/01/70 00:00 | |
This is for the XA which has a UART that | 01/01/70 00:00 |