| ??? 10/06/05 07:52 Read: times |
#102016 - errata? Responding to: ???'s previous message |
hi,
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.
Do you check errata of DS89C420? At the bottom of DS89C420 product folder there are files named "Errata DS89C420". I suggest to read them careful. Some revisions have indicated troubles when entering bootloader and autobaud. For example, revision A1: ---- The auto-baud routine of the bootstrap loader does not always function reliably (observed as garbled information instead of loader banner). Functionality is better at lower baud rates. Experiments show that the maximum reliable baud rate for any given crystal frequency is given by the equation: fOSC / 1152 = Max Baud ---- To enter loader mode, PSEN is sampled after reset is pulled high and EA is pulled low. This dictates that the transition of PSEN from high to low should be delayed from the onset of reset and EA by 8 clock cycles. ----Revision A2: ---- To enter loader mode, port pin P3.7 must be pulled high when the pin combination of RST = 1, PSEN = EA = 0 is applied. When exiting loader mode, port pin P3.7 must be pulled high before the pin combination of RST = 1, PSEN = EA = 0 is released. Regards, Oleg |
| 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 | |
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| 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 | |
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| Lower clock frquency | 01/01/70 00:00 | |
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