Blocks can execute at different rates within the same module using the block scan rate. The block scan rate forces the function block's execution to skip a certain number of scans for that module. By default, function blocks in a module have a block scan rate of one (1). If the block scan rate is one, it is not displayed on the block. You can change the block's scan rate to a positive integer value.
The block scan rate indicates the number of times the module's algorithm is executed compared to the block. For example, if the block scan rate is one, there is a 1:1 ratio. Every time the module scans, the block executes. If the block scan rate is 3, there is a 1:3 ratio and the block is executed every third scan.
If a module's scan rate is 1 second and you set the block scan rate of a block in that module to 5, the block executes every 5 seconds. The block execution skips for four module scans and executes on the fifth scan. The block scan rate of the block effectively multiplies the module scan rate.
Use this feature for cascade control. For example, combine the two loops required for cascade control into one module, as long as the scan rate for the outer loop is a multiple of the scan rate for the inner loop.