On 30 May, 08:29, Philip Herzog <p...@[EMAIL PROTECTED]
> wrote:
> Mike Treseler wrote:
> > Maybe those 8 flops are wired up like a ****ft register.
>
> I'm pretty sure they were, but that's the whole point: That uses 8
> flops, but if the ****ft register was extracted and packed into a LUT I'd
> only use one LUT. This makes a difference for me, since I need many of
> them...
>
> - Philip
> --
> I will always be puzzled by the human predilection
> for piloting vehicles at unsafe velocities.
> (Lieutenant Commander Data)
A LUT "****ft register" as you call it is not actually a ****ft
register, rather it is a delay function. You cannnot tap off it. The
Unisim library contains an element "SRL16", which will implement a 1
bit ****ft register that takes 1 lut, with a delay of between 1 and 16
clock cycles. It uses 1 Lut and 1 register.
The problem with delcaring it as a vector of length 16, it implies
each bit is a register, and you have access to each bit individually.
Unless the synthesiser analyses the registers and finds none of them
are tapped, and is clever enough, it will most likely create a string
of registers.
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