| ??? 02/12/07 01:01 Read: times |
#132568 - ...as engineer? Responding to: ???'s previous message |
Jan said:
Good point, but I still cannot see why shouldn't be used as a PLL reference. Because of what I stated here: Jan said:
A third reason not to use ALE as a clock signal is the rather unpredictable performance of ALE, when having a micro providing extended internal RAM or internal EEPROM. These memories are mostly accessed by MOVX instructions and you can never know whether the actual mirco let one ALE skip or not. This is not only a problem with Atmel, but with some other manufaturers too. Jan said:
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. This assumption is so fundamental, that there's no need to be stated in the datasheet explicitly. Jan said:
Ooooh, so you DO omit the external reset... :-) Read carefully what I wrote: Kai said:
And with an ATMEGA we had severe problems with the internal POR some months ago... I wrote "we" not "I", simply reflecting the fact, that I'm not alone in our company. Needless to say, that we added an external reset in the meantime. Jan said:
...but a good chip failing only rarely in a bad design ensures the good design will work OK even under marginal/extreme conditions. Sorry, but your fantasy formula doesn't desdribe reality very well... Kai |
