If a Boolean parameter is used to differentiate between 2 operating mode or 2 states of a function block, its name often has the following form: mode1_mode2 (example: MANU_AUTO, SP_RSP). It is usually specified that the mode1 corresponding value is 0 and the mode2 corresponding value is 1. If for example the MANU_AUTO parameter of a function block is 0, the function block is in manual mode. It is in automatic mode when MANU_AUTO is equal to 1.