Using <ap_fixed.h> to save space

I want to port a program from C to RTL that includes a 283*696 array of floats. Unfortunately, this is too big for the BRAM to handle. I realize that this would introduce a loss of precision, but would it be reasonable to use a declared fixed data type in order to save space? Note that the precision of the floats is never past the 10,000ths in decimal, and never greater than 7 in decimal as well. Is this a feasible implementation if I'm currently about 150% above my alloted BRAM for my device?

0 drozwood90 over 9 years ago

Sounds like you are a bit new to using RTL. A rule of thumb I use is to keep all resource use 80% or less. That helps allow the tool to allocate the proper resources to the right places while meeting timing.
If you are 150% overloaded, my suggestion is, if you can use HDL. That can handle the floats with only some effort on your part. If that is not an option, I would suggest you use the DDR memory. You can use AXI structures to access that memory. This way, you can just access the values that you need at the time that you need them, instead of trying to load a HUGE structure into the BRAM - which should be thought of similar to a register inside a Microchip. It is not something that you want to just arbitrarily fill!
--Dan
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