Command: Pause a cog's execution until I/O pin(s) do not match designated state(s).

((PUB ┆ PRI))
   WAITPNE (State, Mask, Port )

• State is the logic state(s) to compare the pins against. It is a 32-bit value that indicates the high or low states of up to 32 I/O pins. State is compared against either (INA & Mask), or (INB & Mask), depending on Port.
• Mask is the desired pin(s) to monitor. Mask is a 32-bit value that contains high (1) bits for every I/O pin that should be monitored; low (0) bits indicate pins that should be ignored. Mask is bitwised-ANDed with the 32-bit port's input states and the resulting value is compared against the entire State value.
• Port is a 1-bit value indicating the I/O port to monitor; 0 = Port A, 1 = Port B. Only Port A exists on current (P8X32A) Propeller chips.

Explanation

WAITPNE, "Wait for Pin(s) to Not Equal," is one of four wait commands (WAITCNT, WAITPEQ, WAITPNE, and WAITVID) used to pause execution of a cog until a condition is met. WAITPNE is the complimentary form of WAITPEQ; it pauses the cog until the value of Port's I/O pin states, bitwised-ANDed with Mask, does not match that of State.

When executed, WAITPNE activates special "wait" hardware in the cog that prevents the System Clock from causing further code execution within the cog until the moment the designated pin, or group of pins, does not equal the designated state(s). The wait hardware checks the I/O pins every System Clock cycle and the cog's power consumption is reduced by approximately 7/8^ths during this time.

Using WAITPNE

WAITPNE is a great way to synchronize code to external events. For example:

waitpeq(%0100, %1100, 0)         'Wait for P3 & P2 to be low & high
waitpne(%0100, %1100, 0)         'Wait for P3 & P2 to not match prev. state
outa[0] := 1                     'Set P0 high 

The above code pauses the cog until P3 is low and P2 is high, then pauses the cog again until one or both of those pins changes states, then it sets P0 high.