[time-nuts] SiLabs

[Randy Warner]

Didier,

I too have looked at the SiLabs parts. I may just have to get one of
their eval boards.

I use the SiLabs CP2102 USB-to-Serial converter in my new receiver Eval
Boards. Tiny little thing, no external components, and it also has the
ability to handle more than just RxD and TxD traffic. That was always a
problem with the FTDI USB converter in that you could not put the 1PPS
out on the USB bus. A lot of times I ended up using the USB just for
power and used the serial port for comms. Seems like an awful waste of a
USB connection. Anyway, with the 2102 I can put a the 1PPS on a
"virtual" DCD line and keep TAC32 happy.

Randy

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-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Didier Juges
Sent: Tuesday, August 08, 2006 7:50 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Frequency Dividers

I have used a number of pll controlled microcontrollers, and I would not
recommend using one of those in a timing application such as those
discussed here.

These PLLs are generally not very clean spectrally (it's actually a good
thing for EMI, some chips have purposeful spread spectrum clocks) and
may have lots of jitter.

However, most of the chips with PLL will let you disable the PLL and run
from a crystal or an external oscillator. Alternately, it you use the
timer instead of software loops, you can run the core from the PLL as
long as the timer itself is not driven from the PLL.

I use the Silabs C8051F133  in several projects and it will run with up
to a 100 MHz clock (with many instructions running in one clock cycle)
from the PLL or I believe 50 MHz with an external oscillator. And if you
needed a 16 x 16 MAC engine for that counter, it has that too :-)

http://www.silabs.com/public/documents/tpub_doc/dsheet/Microcontrollers/
Precision_Mixed-Signal/en/C8051F12x-13x.pdf

That's not your father's 8051!!!

For timing applications, it has 5 general purpose 16 bit timers and a 6
channel 16 bit Programmable Counter Array, so by using one of the 16 bit
timer as a prescaler for the PCA, you can have create up to 10
low-jitter timer outputs with 6 of them having up to 32 bits capacity,
with minimum software overhead, so the CPU is mostly available for
anything else you might want to do with it..

Pretty neat, uh?

The other day, a rep for a well known semiconductor/microcontroller
company that shall remain nameless was showing me their latest ad for an
8051 running at 50 MHz with a 4 clock core and in big letters: FASTEST
8051 AVAILABLE. I pointed him to the Silabs web site and left him
there...

Didier KO4BB

PS: only problem for the hobbyist, it only comes in a surface mount 64
or 100 pins TQFP (cheap development boards are available, with JTAG
programmer, prototyping area and serial interface). I am not associated
with Silabs, however I am a very satisfied customer and I can recommend
their products (hardware and software), they are topnotch and Silabs
customer service is excellent. I routinely use them in products that
operate way outside the generous -40 to +85 C temperature range without
any problem.