On 30/04/2011 19:34, V G wrote:
>   But I don't understand what a "reg" does and
> what it really does inside the chip.

A reg is short for register, e.g. a place to store bits, usually one or=20
more D type flip-flops.
This is the basis of sequential (as opposed to combinational) designs=20
(if your knowledge of digital design is rusty, read a book on it, you=20
need to know this stuff well for FPGAs)
When you compile your design, have a look at the "schematic" in ModelSim=20
(or whatever Xilinx uses)
This is a graphical representation of your design.
You will be able to see what different verilog constructs turn into on=20
the chip. I found this quite useful for getting the hang of visualising=20
what my Verilog is doing, and when to use what construct.
Try and keep it reasonably simple though, otherwise it will be difficult=20
to read easily. You might be surprised what a couple of statements can=20
turn into.
Try things like seeing what an addition of two registers becomes, and=20
compare a case statement to an if else statement. Pong Chu's book goes=20
into things like priority routing and much more, so it should all make=20
sense soon enough if you keep at it.


--=20
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