What is the difference between a single process shared variable and a single process shared variable with real time single element FIFO enabled.

[mattyG]

When configuring a single-process shared variable, what happens when I select the "enable real-time FIFO" option and I select "Single Element"?

It is not really a FIFO because it only has a single element. So what is the difference if activate or don't activate the RT-FIFO (single element) option? 

[Amanda_H]

Hi Matty,

You can change the array size of this "single element" so that it contains multiple elements. Does this help?

[mattyG]

Hi,

No, I don't want multiple elements.

My question is "What is the difference between a single process shared variable and a single process shared variable with the real-time FIFO (single-element) option enabled.

What functionnality does it add to the shared variable? Why does this option exist?

Regards,

Matt

[GerardoG]

Matt,

The single-process shared variable (non RT FIFO) is basically a global variable, while the RT FIFO version uses a different mechanism to pass data, similar to the RT FIFO VIs. The RT FIFO version is designed so that a reader will not block a writer or vice versa. This allows you to have a time critical thread that writes to the variable and a different thread that reads from it without causing resource contention. The non RT FIFO variables have protection built-in, that is, they if you are reading in one loop it will block any other access to that variable.

I hope that helps. You can read more about shared variables here.

G