Lookup table in cogmem (propgcc)

byrtolet

Hello,

I want to use a lookup table, which is situated in the cog memory (to be as fast as possible).
I'm using propgcc and I am not able to declare an array as a _COGMEM.
Is this possible in propgcc? Is it possible at all (with assembler)?

Tracy Allen

A lot depends on what you want to do with the data, but in assembler (psam) it is certainly possible. I can't help with propgcc. The value to read comes from a mov instruction..

rdval                   mov     value, 0-0

where the 0-0 is a placeholder for the source address. That source address gets put there by a movs instruction somewhere else in the code...

movs rdval, my9bitSourceAddress

That is, self-modifying code. It might be part of a loop that steps through values of my9bitSourceAddress, or my9bitSourceAddress might come from a command of some sort. Here is a helpful snippet from JonnyMac.

byrtolet

Tracy Allen,
thank you for the reply!

Rayman

Just FYI... One way to make it as fast as possible is to start your table at memory location #0 (I.e, the bottom of cog ram).
It's a bit of a trick, but then you don't need to add in the offset to the table...

byrtolet

Rayman, great suggestion, thanks!

Does anyone knows why we can't do this in propgcc?

Rayman

If I remember right, you can write the driver in Spin and then us Spin2GCC to create a binary file that you can load inside GCC...

Tricks like the one above would probably require doing this...