Need to help to understand flow of ladder logic

[nbn2015]

Hello Everyone, I am new to ladder logic, and trying to understand flow of below attached ladder logic- How does the program flow ? Does PT4601_I in rung 3 waits for rung 2 to complete inorder to consider updated value of PT4601_I or it consider PT4601_I default value and runs simultaneously with rung 2 ? Thank you in advacne

[Steve Bailey]

Each rung is executed sequentially. When a variable's value is updated as a result of an instruction on rung 2, the updated value is immediately available at rung 3. What is the full name of the variable at the IN1 node of the ADD_REAL instruction on rung 3? If it is PT4601_INT and that variable is defined as INT, then you may have a problem mixing an INT variable with a REAL instruction. If PT4601_INT is actually a REAL variable then you have a problem with the REAL_TO_INT instruction on rung 2.