An incorrect execution order of module function blocks can make the module appear to scan slower than its actual scan rate.
Input blocks should execute before control blocks or output blocks. The default execution order is based on the order the blocks are created. Note the execution order of the blocks in the bottom right of each block and change as needed.
For example, consider the INTERLOCK_D input of the Device Control function block or the TRK_IN_D input of the PID function block. These values might be used by the blocks to stop a motor or close a control valve. If the Device Control or PID block executes before the block(s) that determine the value of the input, the module loses a scan before acting on the input. For more information, refer to the section entitled Set the Execution Order of Function Block in the Control Studio help system.