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-   -   Re: Signal/Variable Initial Vaues and Evils of Asynchronous Reset (http://www.velocityreviews.com/forums/t724394-re-signal-variable-initial-vaues-and-evils-of-asynchronous-reset.html)

Mike Treseler 05-29-2010 10:21 PM

Re: Signal/Variable Initial Vaues and Evils of Asynchronous Reset
 
Wendigo wrote:

> "When you give a register an initial value in a declaration, XST sets this
> value on the output of the register at global reset, or at power up. The
> assigned value is carried in the NGC file as an INIT attribute on the
> register, and is independent of any local reset."
>
> Are there certain vendors that don't support this? Is it not
> supported by certain technologies? (ASICs, perhaps?)


That is how brand X does it.
Keep in mind that an FPGA doesn't do anything
at power up until the image is successfully loaded,
and even then, a "non-evil" synchronous reset won't do
anything until the clock is running.

> Can the GSR signal (Global Set/Reset, I'm guessing this is a
> vendor-specific term) be used for synchronous reset?


No. It is brand X only, and isn't an input.
Better than nothing, but not often adequate.

-- Mike Treseler


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