Using the GNU Compiler Collection (GCC): PRU Built-in Functions

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#### 6.60.27 PRU Built-in Functions

GCC provides a couple of special builtin functions to aid in utilizing special PRU instructions.

The built-in functions supported are:

`__delay_cycles (long long cycles)`

  This inserts an instruction sequence that takes exactly cycles cycles (between 0 and 0xffffffff) to complete. The inserted sequence may use jumps, loops, or no-ops, and does not interfere with any other instructions. Note that cycles must be a compile-time constant integer - that is, you must pass a number, not a variable that may be optimized to a constant later. The number of cycles delayed by this builtin is exact.

`__halt (void)`

  This inserts a HALT instruction to stop processor execution.

`unsigned int __lmbd (unsigned int wordval, unsigned int bitval)`

  This inserts LMBD instruction to calculate the left-most bit with value bitval in value wordval. Only the least significant bit of bitval is taken into account.