| ??? 04/18/07 04:57 Modified: 04/18/07 04:59 Read: times |
#137401 - That\'s not what I said ... Responding to: ???'s previous message |
Avishek Kumar said:
First of all I am sorry to return late.
1) I am using Dallas DS89C430 microcontroller. I am using an external xtal OSCILLATIOR of 33MHz. What I want to ask is this--- What value of resistance must be connected between xtal OSCILLATIOR's output pin3 and the input pin of microcontroller i.e xtal1. Where did you get the idea that a resistor is required? I doubt it will damage anything, but why would you use one? 2) Another interseting point which came in this discussion is that -- is it possible to connect a resistance between xtal1(i.e xtal1 input pin of microcontroller) and xtal2(i.e xtal2 output pin of microcontroller). What purpose will it serve? Can we get an output frequency from xtal2 pin of controller without giving the input at xtal1? What frequency would you hope to obtain from Xtal2? 3) I do not know the chip you use, but if it has internal code and data memory and you run off it, there may, correctly, be no ALE. My chip is a DS89C450, which is essentially the same as the DS89C430 but with more FLASH on board. As i said the chip is DS89C430. Do u mean to say that if we try to access the internal code and data memory beyond the chip supports, there will be no ALE? No ... what the datasheet says is that you can, if you wish, configure the SFR's such that the chip will produce ALE only when it accesses external memory-mapped resources. If you don't do that, intentionally or otherwise, it is supposed to produce ALE. Suppressing ALE is an effort to reduce EMI. What the datasheet says about Xtal1 and Xtal2 is, " Crystal Oscillators. These pins provide support for fundamental-mode parallel-resonant AT-cut crystals. XTAL1 also acts as an input if there is an external clock source in place of a crystal. XTAL2 serves as the output of the crystal amplifier." That's pretty clear. I guess you could infer from that, that Xtal2 can be used as a buffered output of the signal that comes in on Xtal1. I'm not sure that you would want to do that, as there's no specification for what that buffered output can/will do. RE |
| Topic | Author | Date |
| DS89C430 - - - - -- ALE SIGNAL | 01/01/70 00:00 | |
| Please explain... | 01/01/70 00:00 | |
| explained here | 01/01/70 00:00 | |
| please explain | 01/01/70 00:00 | |
| he probably uses an external crystal oscillator... | 01/01/70 00:00 | |
| Oscillator Feedback Resistor | 01/01/70 00:00 | |
| a thought and a question | 01/01/70 00:00 | |
| There will be ALE on MOVX cycles | 01/01/70 00:00 | |
| pls read this | 01/01/70 00:00 | |
| That\'s not what I said ... | 01/01/70 00:00 | |
| Is this all about 'running without a crystal'? | 01/01/70 00:00 | |
| still at same stage | 01/01/70 00:00 | |
| Please explain ... What do you mean? | 01/01/70 00:00 | |
| Reflections upon your described predicament | 01/01/70 00:00 | |
| do you think he's using a 'scope? | 01/01/70 00:00 | |
| The rigth person | 01/01/70 00:00 | |
late response ... | 01/01/70 00:00 |