[time-nuts] Frequency Dividers

[SAIDJACK at aol.com]

In a message dated 8/9/2006 20:29:22 Pacific Daylight Time, didier at cox.net  
writes:
 
Hi Didier,
 
yes, its great fun to use, and much easier as well (SRAM  addressing in 8051 
- yuk)
 
BTW: I measured the 1PPS output jitter (generated by an LPC "Match"  output 
pin driven by an internal 60MHz PLL) on my Wavecrest DTS-2070C  Jitter 
analyzer: it's about +-100ps. This is equal to +-1E-010 per second  stability.
 
Then I measured the 1PPS output of my SRS PRS-10 Rubidium standard: it has  
about +-120ps jitter! Wonder what the best CMOS dividers can do.
 
On Digikey, the LPC2101 Arm is $3.15 for a single piece, and the SIL  
8051F310 is >$6 for one! Tough choice. The 8051 does have one big  advantage: it is 
cycle accurate, and fun to program in assembly. The Arm is  really a "C" 
device, somewhat tough to program in assembly.
 
There is a lot of public domain info and software on the Yahoo LPC2000  
discussion group: _http://groups.yahoo.com/group/lpc2000/_ 
(http://groups.yahoo.com/group/lpc2000/) 
 
Keil also supports the LPC Arm out-of-the-box with ready-made examples; I  
think you can get an eval version for free.
 
For timing apps, the Arm has much better timer/counters/Capture-and-Match  
units than the 8051's.
 
bye,
Said

Thanks  for the info, I did check the Philips (and Sparkfun) web site(s) 
and I  must admit the ARM chip is cheap and has impressive 
specifications. With  the GNU tools, I know it will work and it will fit 
my homebrewer's budget  :-) I used to consider $99 for a development kit 
cheap, but $29 beats it  with good margin.

At that price, I don't see how I could pass on a  chance to evaluate it, 
if not for the fact that I have so much 8051 code  (and a Franklin 
compiler, wich is similar to the Keil)

I agree that  the Silab chips are somewhat expensive, at least for high 
volume consumer  stuff. However, I do not consider 64k of Flash memory 
(and several kB of  RAM for most parts) as small for an 8 bit micro, but 
there again, if you  are considering applications that require large 
buffers, such as data  compression, you probably would not want to use an 
8 bit chip anyhow.  Also, on the 8051, addressing RAM above the customary 
128 bytes of DATA  space (XDATA) takes a lot longer. On the 8051,  RAM is 
not always  equal :-)

Thanks again.