Is my lookup table with 50,000 entries too big for MCU memory (dsPIC33EP256MC506)?

Question

I want to implement a 2-input 1-output fuzzy logic controller using lookup table on the dsPIC33EP256MC506 microcontroller. I am comparing the lookup table and actual fuzzy logic controller side by side in Simulink. In order to minimize the error between the lookup table and actual controller, I am having to generate a huge table, having around 50,000 entries. The input 1 range is -5000 to 5000, input 2 range is -1000 to 1000 and output range is -9999 to 9999. I am using Simulink code generation.

I went over the datasheet's memory section, but still need some expert guidance in relating the lookup table size to the program memory size. My questions are: how can I find out if this lookup table will fit into the program memory? How can I estimate the approximate size of the lookup table? What are key things to look for in datasheet or the lookup table from practical implementation viewpoint?

Answer 1

You say your lookup table will contain 50000 elements and each element will have the range of -9999 to 9999. That means each element will need 16 bits (= 2 bytes) of memory. So the whole LUT will need 50000 x 2 bytes = 100000 bytes = aprox. 97.6 Kbytes.

Your microcontroller has 256 Kbytes of Flash memory and 32 Kbytes of RAM. So your program/Flash memory would be enough for the LUT. To place the table in program memory you need to declare it as const: const int16_t LUT[] = { ... };