| ??? 03/10/06 08:03 Read: times |
#111846 - Re: AT89S8253 Responding to: ???'s previous message |
hi,
Trevor Jacobs said:
I had a problem with the AT89S8253 a while back. Since Atmel has changed the specs on the clock oscillator loading (see the January data sheet), you can really only use up to about a 16MHz crystal externally and have it start up correctly every time.
Did you try oscillator chip instead crystal? In projects where startup stability is important subject (perhaps for most projects here I work at), usage of oscillator instead crystal, and external power supervisor instead RC-reset are very welcome. BTW it will run on a 24 MHz external clock at X2, but I don't know how reliable that is. I agree with Jan and Kai on this. Probably safer to limit it to 24 MHz total.
It seems so. The thing which confuses me has been highlit by Erik: Erik Malund said:
I, fortunately, can not answer to what Atmel does but the Philips 89C51Rx2 states max 20 MHz in 6 clock mode, max 33MHz in 6 clock mode. I have no idea how well this may relate to the Atmel part, but maybe looking at the Atmel Rx2 datasheet could provide a clue.
So looking at other Atmel X2 devices I see that, for example, AT89C51RD2/ID2/AC3/CC03 etc do allow: 60MHz in standard mode; 30MHz in X2 mode. Comparing frequences it seems like S8253/S2051/S4051 allow 24MHz in X2 mode and about 50MHz for standard mode (wow! :) But as this fact is not indicated in their datasheets so probably other limit takes place: 12/24MHz respectively. I definetly wouldn't design a commercial product with higher than a 12 MHz clock running X2.
Why not? We do some products where external oscillator modules at 18.432MHz and 22.1184MHz are used together with AT89C51CC03 and AT89C51ED2 derivatives. No return due for 2000+ over three years. I haven't used the S2051 or S2052. Checkout the new AT89LP4052, it's a screamer! Sure and they are sparse here even not expensive: C2051 0.97 USD S2051 1.13 USD LP2052 2.11 USD In fact for this project I do for now, I need not with productivity of MCU. Instead it, I have been asked to use 18.432MHz oscillator by customer. So I do select X1 mode. Single cycle core! I've been having lot's of fun with it. PWM's work great too. I only wish it had 1 more timer,as it takes a timer per PWM port. I was looking at this for microstepping stepper motors... As Erik already said for powerful projects like this we use SiLabs F120/130. Regards, Oleg |
| Topic | Author | Date |
| AT89Sxxxx with X2 - max.freq | 01/01/70 00:00 | |
| mess | 01/01/70 00:00 | |
| a comparison | 01/01/70 00:00 | |
| Assuming... | 01/01/70 00:00 | |
| AT89S8253 | 01/01/70 00:00 | |
| more like a whisper | 01/01/70 00:00 | |
| Not for under $2 in low quantities... | 01/01/70 00:00 | |
| Not for under $2 in low quantities... | 01/01/70 00:00 | |
| Why always... | 01/01/70 00:00 | |
| no Atmel beating here | 01/01/70 00:00 | |
| Ok | 01/01/70 00:00 | |
| Mature? | 01/01/70 00:00 | |
| Re: AT89S8253 | 01/01/70 00:00 | |
| various cores | 01/01/70 00:00 | |
| RE:AT89S8253 | 01/01/70 00:00 | |
| AT89C5115 | 01/01/70 00:00 | |
| more timers | 01/01/70 00:00 | |
| > Got a feedback from Atmel now? | 01/01/70 00:00 | |
be patient I`ll report | 01/01/70 00:00 |