| ??? 02/12/07 00:19 Read: times |
#132564 - speaking from experience... Responding to: ???'s previous message |
Kai Klaas said:
The reason, why ALE should not be used as a standard clock signal, is that ALE can be unsanely noisy. Good point, but I still cannot see why shouldn't be used as a PLL reference, with appropriate care. The real point is, that the datasheet does not specify exactly the behaviour of ALE. An another point is, that Atmel claims the 8253 is a drop-in replacement of a quite popular 8252 - which apparently is not true, for various reasons. Kai said:
Means, the manufacturer assumes a well regulated 5V supply,[...] Again, if the manufacturer assumes anything, he should face the consequences. There are enough other '51 manufacturers and other cheap 8-bit microcontroller manufacturers who don't assume as much. The funny thing is, that among those belongs... Atmel... with the AVRs. Jan said:
Kai, please, this chip IS proven to be a crap. Kai said:
Jan, not so fast. Many of the actual bugs are a consequence of the original Intel's 8051 design. The vulnerability of this micro to improper reset, Vcc noise, capacitve loading on port lines and Vcc power-up rise time are direct consequences of the orignal design. This chip is apparently a redesign with a new core (as indicated by serious problems with the serial flags), different process (indicated by strange crystal capacitor values) etc. So, they kept the old problems and added new? Shall I be impressed by this? :-) Jan said:
Look at AVRs and PICs. They are competition to '51s - and, although I don't like to tell it, they ARE competent. Kai said:
Really?? I found nearly as many errata for AVRs and PICs as for 8051 micros. Infact, I once intended to use a PIC but kept my fingers off, because the datasheet missed many many important details and the errata read like a horror story. And with an ATMEGA we had severe problems with the internal POR some months ago... Ooooh, so you DO omit the external reset... :-) I have yet to see an AVR which cannot by programmed by the rusty nail method. I even never saw an AVR not working without external reset - although they are all not our design, I still insist on proper reset circuit. And the price/performance is unbeatable in many cases, the features set is impressive, hard to find an application which they don't fit. The only trouble is that I don't like them... PICs are the same, they are making me nausea... Kai said:
And I cannot understand, why people take an immature micro. I wouldn't call immature a micro being in revision R (mind, that's around 20 revisions, if they did not slip in A1, A2 etc...). I don't say one does not have to strive for as perfect board design as possible; but a good chip failing only rarely in a bad design ensures the good design will work OK even under marginal/extreme conditions. Contrary, if you take the crap and try to make it happy, any slight external disturbance which you sometimes simply cannot avoid will burn it out... Jan Waclawek |
