Freescale fractional clock divider paper

bitrex · 2017-11-28T18:25:54+00:00

This looks interesting but I'm having trouble deciphering how it's actually supposed to work due to poor tech writing/diagramming on the part of the authors. Can anyone explain how this system is actually supposed to work or what a real-world FPGA implementation might look like?

Nov 28, 2017 24 Replies

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Rob 8 years ago

Well, our CCTV system in the building is now completely IP. True it is not real-time, but it is much more flexible: instead of requiring a dedicated coax from every camera to the "recorder" box, and a power connection at each camera, it now uses an ethernet network with 801.11AT PoE and every camera is only wired to the closest switch. (and it can be done over WiFi when desired)

It is not related to internet, the camera's and the recorder are on an isolated VLAN that has no link to internet. (those devices are to insecure to connect them to internet, especially from the company network)

The picture is Full HD, a big improvement over the old PAL based system. (which of course was better than an NTSC based system)

The only point that holds is that it is not real-time. There is a delay of 1..2 seconds.

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Rob 8 years ago

RF-modulated composite is of course even worse than direct composite video, but for color the difference is small. The limitation of the picture quality is mainly in the standardized parameters of NTSC (or PAL). For BW video the extended bandwidth of a direct composite signal would help, but of course the small number of lines limits the vertical resolution.

Where I wrote "composite" in the posting upwards from this one (not quoted above), I meant to write "component". Another standard that provides better quality than NTSC/PAL composite. It works over similar distances but of course requires 3 coax cables.

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Jim Thompson 8 years ago

[snip]

A programmer of FPGA's wouldn't know how to do that with an XOR plus a D-Flop... without there being specifically "an edge-detection functional block"?? ...Jim Thompson

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bitrex 8 years ago

I haven't really used FPGAs/PALs/programmable digital hardware before. First time for everything, right?

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Michael A Terrell 8 years ago

Maybe the question needs fixed? Most of the broadcast NTSC color equipment had a 14.318180 MHz crustal that was then divided down to every needed signal National Semiconductor even mad a simple color sync generator IC. It used 14.318180 MHz/7 for it's reference, but it provided all of the snc and balnking signals needed for color TV cameras.

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