Hi
I wanna use an external function generator to feed the FPGA with the clock signal. I have come across a function generator from TTi (TG330).
So I am wondering if this device is suitable to generate a stable clock signal or if I will run into trouble.
Maybe there are other, better devices out there that I could use for my purposes? I wanna run the implementation at a very low frequency of around 1 MHz.
Thanks!
I use a TI eZ430-F2013 USB development kit as a clock generator in my lab. This MSP430 processor has a programmable clock on-chip and you can configure the chip very simply to emit the clock signal on a digital output pin. You do need to code a little program, though
-- no nice front panel as on a function generator, but also much cheaper. I got my device free from a TI promotional seminar...
HTH,
--
Niklas Holsti
Tidorum Ltd
niklas holsti tidorum fi
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You do not need anything fancy to clock the FPGA. You can use any crystal oscillator for about $1 and you can divide the frequency down with a few internal flip-flops. You can also build an oscillator with two external resistors plus a capacitor (see my 'six easy pieces"),which is remarkably stable. It all depends on your requirements... Peter Alfke
It's not suitable. The maximum output frequency is given as 3 MHz whereas a typical FPGA clock frequency would be in the 50-100MHz region. You can multiply clock rates internally with a DCM (Xilinx; Altera has a roughly equivalent PLL); but the Xilinx DCM typically works with input frequencies above 25 MHz.
Even if you don't need any performance from the FPGA and a 3MHz clock is sufficient, I'd be worried about the very slow "< 100ns" edges this thing claims to generate. Slow ramps like that, in the presence of noise, can generate several clock edges where you only wanted one. If you MUST use it, feed it through an external buffer to the FPGA.
Go with Peter's suggestion or Niklas's; or wire up the four corner pins on a DIP14 socket and you can plug in any crystal oscillator you want.
- Brian
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