Hi all, I have come across these two acronyms OGSL and EHSL and I do not know what they means. They are used relating to data transmission so by deduction I think that OGSL stands for "Optical G serial Link" but I have no clue on the "G". When mentioning EHSL they talk about copper wires, so it could be "electrical High Speed Link". This is definitely relating to the physical layer. Any ideas? Best regards Luis -----Original Message----- From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf Of Vasile Surducan Sent: 03 December 2007 05:31 To: Microcontroller discussion list - Public. Subject: Re: [EE]: PLL-based Radio 4 timecode data decoder On 12/1/07, Philip Pemberton wrote: > Hi guys, > In a bout of utter madness (well it couldn't really have been anything > else) I decided to pad out a Farnell order with a few (um... 25) heavily > discounted 4046 PLL chips whose only sin is that they contain substances the > Eurocrats don't like. Seeing as I've got some PLLs now, I figured I'd > resurrect my semi-abandoned Radio 4 "LF Radio Data" decoder. > > For those who don't know, BBC Radio 4 carries a data stream that's > phase-encoded onto the carrier wave. All the gory details are in BBC tech > report BBC RD 1984/19 > (). Basically, the > data is biphase (Manchester) encoded, then every shift from 1->0 or 0->1 > causes a phase transition in the carrier. > > What I want to do is detect those phase transitions. I got this idea from > Freescale application note AN1597 > (). > Basically, you wait for a phase transition, set a timer running, then wait for > another Ptran, stop the timer, reset it and kick it off again. A combination > of the previous decoded bit and the time delta gives you the next one or two bits. > > The problem: Getting the "phase transition" pulse to begin with. > > What I have now is a 4046 PLL on a breadboard, with the following VCO > component values: > C: 330pF > R1: 47k > R2: 12k > > And an RC loop filter with R=10k and C=100nF. > > What I'm seeing is a continuous phase shift between the PLL and Radio4. It > seems to lock for a few hundred milliseconds, then kicks out and the Phase > Pulse output (pin 1) pulses for a bit. Then it settles down and works again. The PLL goes out from the lock range. Maybe the capture range is equal (or a bit lower than) with the lock range ? Read on page 9/13 and compute your passive components like it said: http://bertrik.sikken.nl/bat/pdf/4046.pdf > If I wire the PLL input to my Hameg function generator (rigged for 198kHz) > I get a perfect lock. No pulses on pin 1 at all after the PLL locks in. The > attached image illustrates this pretty well - yellow trace is VCO_OUT (4046B > pin 4), cyan is the input signal from the Hameg (4046B pin 14), magenta is the > voltage at VCO_IN (pin 9) and green is the signal from the PHASE_PULSES output > (pin 1). > > Are there any PLL gurus (or builders of Radio 4 data decoders) here that > can suggest anything? > > Based on my limited knowledge of PLLs (most of it from > ), I *think* the loop time > might be too slow. If I'm looking for a single out-of-phase pulse, then I need > the PLL to follow the phase of the signal when it changes, and output a > phase-pulse when it has to make a correction... Or am I thinking the wrong way > round here? > > And before anyone asks, I'm doing this because it looked like a fun > project, and I figured it'd be a good way to practice with the new TDS2024B. > And learn a bit about PLLs too. :P > > Thanks. > -- > Phil. | (\_/) This is Bunny. Copy and paste Bunny > piclist@philpem.me.uk | (='.'=) into your signature to help him gain > http://www.philpem.me.uk/ | (")_(") world domination. > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > > > -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist