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<div class="moz-cite-prefix"><br>
if it's a straight lookup table which you provide with one value
and you get one out, eh,<br>
not one of those here? If 8bits width is enough... perhaps not.
IDK whether there are broader width parallel EEPROMs out there.<br>
<a class="moz-txt-link-freetext" href="https://www.microchip.com/design-centers/memory/parallel-eeprom">https://www.microchip.com/design-centers/memory/parallel-eeprom</a><br>
<br>
I guess you could use SRAM and write to it at startup with your
one MCU and then disengage a bus driver for it (hi Z state) and
enable a bus driver for the actual application.<br>
But the input bit width may not be large enough, one of the
highest available SRAM I've seen was 512KB ~ 9bits. (Though, the
*output* word bit width could always be increased by using several
RAM chips in parallel - all on the same address lines, but the
outputs will each be another byte of the whole word at the same
input address)<br>
<br>
Or learn FPGA logic design, use some small cheap Lattice FPGA, for
which, IIRC, an open source tool chain exists and you don't have
to dish out crazy dough.<br>
(but invest quite some time learning, of course)<br>
With that you can implement a more complex logic and make it react
to your inputs to your hearts content.<br>
<a class="moz-txt-link-freetext" href="https://www.tindie.com/products/tinyvision_ai/upduino-v30-low-cost-lattice-ice40-fpga-board/">https://www.tindie.com/products/tinyvision_ai/upduino-v30-low-cost-lattice-ice40-fpga-board/</a><br>
<br>
That thing's internal configuration memory is only one-time
programmable IIRC.<br>
But also IIRC, it can use an external SPI flash to hold & read
from the configuration data.<br>
The above board has a flash on it.<br>
<br>
As for constant delay:<br>
I am not an FPGA guy myself (on the loooong TODO list, sigh),
others may correct me, but from my limited grasp of FPGA I'd say,<br>
you can trim the delay time of your different logic functions.<br>
Either if you make more complex functions more parallel, but a
similar run-through time through the maximum length path, compared
to the simpler functions.<br>
Or (perhaps not optimal...) add artificial delay to the simpler
functions to even it out.<br>
<br>
<br>
<br>
Am 02.08.2020 um 11:44 schrieb Spiros Makris:<br>
</div>
<blockquote
cite="mid:CAGbpyRdvU+9d0hHBdOZrrapLPvKHYtwioyLfs8eB5sfhGYQ08w@mail.gmail.com"
type="cite">
<div dir="ltr">I am prototyping an application that is based
around the concept of using LUTs to calculate logic functions.
<div>So far I have successfully demonstrated the concept using
an atmega328 and the computational delay is within "specs"
(still quite vague). One of the advantages is that this delay
is constant regardless of function complexity. However,
introducing the user control hardware also adds a new delay
which, although small, is now variable.<br>
</div>
<div>While the concept will work fine for control signals with
delays up to 100-200us, my goal is to extend the operation up
to the audio range, hopefully ~10-15khz. In that context, I
think that the valuable delay will manifest as noise in the
output spectrum. Would that be noticeable? I have no clue,
yet.</div>
<div>So I was trying to think of ways to implement the LUT in
dedicated hardware. Ideally, a combinational logic circuit
that will be addressed directly by the inputs and output the
saved value directly, without any other control logic or
sequence required. A second MCU that only does this task and
is controlled via interrupts and serial by a central MCU
(which will support the screen and controls) is one solution I
can think of and it is fairly cheap - however that requires
programming two controllers. </div>
<div>I am not very familiar with the memory offerings in the
market (never really used one). Is there anything that I could
use to implement the above? I thought of using serial in -
parallel out registers and a bunch of multiplexers, but that
needs quite a lot of PCB space and will be fairly expensive.</div>
<div>Any ideas would be greatly appreciated!</div>
<div>Spiros</div>
</div>
<br>
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