On Jun 30, 3:43=A0pm, "Maarten" <no_one@[EMAIL PROTECTED]
> wrote:
> Hi,
> Alternatively =A0you could consider to program a piece-wise-linear
transfe=
r
> function; By limiting the numberof gain factors (i.e. degreeof freedom
in
> choice for steepness) =A0to a set say {4*,2*, 1* , 1.125*, 1.25*, 1.5*}
yo=
u
> can replace multipliers by a number of ****ft-and-add functions, which
> results in a compact and fast (since its most probably video, you should
I think you're missing my point that all of the calculation stuff can
be done in a function that produces a constant. That constant is a
lookup table array. No multipliers, log/exp functions, etc. would be
synthesized.
Functionally, and from a synthesis perspective, it's absolutely no
different than if you were to use Excel to compute the lookup table
values and copy/paste them into your code. The difference is in the
maintainability of the design.
If you go the copy/paste route though your HDL design contains an
array of 'magic' numbers for the lookup table entries that (hopefully)
have some reference back to the Excel spreadsheet that generated
them...and hopefully nobody accidentally changes any of the values
when doing a search/replace operation.
If you go the route of having your HDL compute the lookup table
entries directly then the HDL has a fairly short, easy to read
function that (should) look very close to the true source equations
that define the mapping.
Functions to compute constants are not shackled with the same
constraints that apply to signals.
Kevin Jennings
|
