FIFO as a Logic Analyzer; Clock synthesizer

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nospam 21 years ago

Hi! I have a big FIFO chip covered by dust, that I'd like to finally use. The most useful application I'm imagining for it is to finally make myself a logic analyzer. This FIFO (Texas Instruments SN74V3690-6PEU) is a 3.3V device, but has 5V tolerant inputs. "Great!" I thought.

What I'm asking you is: should I connect the probes (just a header cable) directly to the FIFO, or should I use an high speed buffer inbetween? Consider that the chip is specced at 166MHz.

Moreover, what is the cheapest way to produce a variable clock speed up to 166MHz (and possibly beyond, for other applications)? A PLL? Any chip you may suggest me?

Thanks! TPM

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Amontec, Larry 21 years ago

Why not a CPLD or FPGA. And do your own frequency synthesizer using an accumulator. For high speed accumulator, use pipeline methodology.

Laurent

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Len 21 years ago

Re the clock: If you're going to put a processor in the project that's I2C capable, use the AD9834 to divide down a nice high frequency oscillator to any frequency you want. Analog Devices has a web tool to help you get the hang of programming it, and it's a GREAT chip!

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Good luck! Len

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Len 21 years ago

Re the clock: If you're going to put a processor in the project that's I2C capable, use the AD9834 to divide down a nice high frequency oscillator to any frequency you want. Analog Devices has a web tool to help you get the hang of programming it, and it's a GREAT chip!

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Good luck! Len

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Len 21 years ago

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Eric Smith 21 years ago

Larry Am> Why not a CPLD or FPGA. And do your own frequency synthesizer using an

Both suggestions are DDS (Direct Digital Synthesis). That's great for a lot of things but not so great for producing high frequency square waves. For that, you're much better off with a PLL. You might try the Cypress CY22150 or CY22393/4/5 programmable clocks. They're fairly inexpensive, and available from Digikey.

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For the CY22150, they have a nifty little "Licorice" demo board (CY30700), that only costs $20.

Eric

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FIFO as a Logic Analyzer; Clock synthesizer

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