| ??? 07/19/05 09:15 Read: times |
#97608 - RD2, /PSEN and the joy of being perfect Responding to: ???'s previous message |
I do use jumper pins for ocassional momentary shorting quite often, as they are cheap an take up little space on boards - using a screwdriver, my keys, any thin piece of metal laying around. Ehm, not elegant, either... :-))) I haven't noticed anything on /PSEN active is harmful at powerup - and as dumb people are the happiest as they don't care - I do my "wire" together with powerup for quite a long time now with T89C51RD2, AT89C51ED2 and a P89C51RD2H, with no visible damage whatsoever... My idea is, that they put it into datasheet as some people powered it up without proper reset and being uninitialized it might run as if in external-memory mode with /PSEN being driven hard - and that might perhaps in long run make problems. I wander, too, how can PSEN be damaged while /EA is high, but that's another issue. Nevertheless, if a pushbutton is provided both for /PSEN and RESET, and a description is made for the proper pocedure - "don't hold /PSEN button while powerup, but after, hold it and press RESET button" - or so, I think no harm will be done. The idea with solderpoints and "anti-solderpoints" would be to provide two alternative circuits - one (default) for the Dallas parts and the other (needing disconnecting and connecting a few spots) for RD2s, so that DTR would initiate ISP for both. The RD2 circuit would require disconnecting /EA from xx125 (the jumper to set it high is already there), and to stretch /PSEN beyond end of reset - a simple RC on appropriate xx125's "gate" would do. But if there is a simple way for the /PSEN pushbutton, that's far enough, of course. Jan Waclawek PS. Re the 22 wire - I just wanted to point out that the rest of world does not use the parts of body as measurement units for quite a time... :-D |
| Topic | Author | Date |
| 8052.com SBC | 01/01/70 00:00 | |
| SBC | 01/01/70 00:00 | |
| I'm Interested, but no big hurry | 01/01/70 00:00 | |
| Good point | 01/01/70 00:00 | |
| BTW | 01/01/70 00:00 | |
| I'll update | 01/01/70 00:00 | |
| This is a nice chip when you need pins g | 01/01/70 00:00 | |
| Questioins | 01/01/70 00:00 | |
| elaborations | 01/01/70 00:00 | |
| RD2 programming | 01/01/70 00:00 | |
| Question | 01/01/70 00:00 | |
| RD2 and PSEN | 01/01/70 00:00 | |
| LeDot | 01/01/70 00:00 | |
| solder point | 01/01/70 00:00 | |
| go figure | 01/01/70 00:00 | |
| solder point/LeDot | 01/01/70 00:00 | |
| Jumper/button | 01/01/70 00:00 | |
| datasheet | 01/01/70 00:00 | |
| RD2, /PSEN and the joy of being perfect | 01/01/70 00:00 | |
| I think | 01/01/70 00:00 | |
| Herr Ohm says no | 01/01/70 00:00 | |
| Hands off | 01/01/70 00:00 | |
| no touch | 01/01/70 00:00 | |
| tidbits | 01/01/70 00:00 | |
| AT89S8253 | 01/01/70 00:00 | |
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| single nand gate?? | 01/01/70 00:00 | |
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| Errata | 01/01/70 00:00 | |
| AT89S8253 ISP | 01/01/70 00:00 | |
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| Caps for MAX232 | 01/01/70 00:00 | |
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| Sure! | 01/01/70 00:00 | |
| in that case... | 01/01/70 00:00 | |
| I've got a couple of RD2's | 01/01/70 00:00 | |
| http://www.efton.sk | 01/01/70 00:00 | |
| What about ED2's | 01/01/70 00:00 | |
| yes | 01/01/70 00:00 | |
| Basic 52/RD2 | 01/01/70 00:00 | |
| b52rd2 | 01/01/70 00:00 | |
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Basic 52 | 01/01/70 00:00 | |
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| 125 | 01/01/70 00:00 | |
| RE: '125 and JP4 | 01/01/70 00:00 | |
| Yes position? | 01/01/70 00:00 | |
| Got it - Bad 8253 | 01/01/70 00:00 | |
| No explanation | 01/01/70 00:00 | |
| You were right the first time - my bad | 01/01/70 00:00 | |
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| Memory mapped LCD problems | 01/01/70 00:00 | |
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| Building one | 01/01/70 00:00 | |
| Microseconds? | 01/01/70 00:00 | |
| Scale error | 01/01/70 00:00 | |
| Memory-mapped LCD initialization | 01/01/70 00:00 | |
| Thanks, Craig! It works! | 01/01/70 00:00 | |
| SBC - Manual | 01/01/70 00:00 | |
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