Hardware Input/Output Interface

The following description of process flow of a wired input coming from a plant system describes the working of this interface:

·         The signal is agitated between the input board of the PLC and the plant system.

·         In a first function of software called the “Inputs Wrapper”, the signal is duplicated from an area of I/O addressing to an area of DB addressing, e.g. Input “I0.0” is duplicated to “DB1.DBX0.0”. Note: PLC complete addressing is employed here for better understanding, but signs should be used. Now, the signal becomes a joint DB variable.

·         If the signal is Boolean, the variable goes through via a layer of “Anti-Rebounce”.

·         The joint DB variable is transferred to a block of “Interface Switch” where the judgment is made to utilize the signal coming from a simulator or a wired signal. Another joint DB variable is issued.

·         The joint DB variable issued is transferred to an “FBS Wrapper”, where the variable is duplicated from a component naming convention to an FBS Level 3 convention or FBS-L3.variable. Another joint DB variable is issued.

·         From the “FBS Wrapper”, the joint DB variable can be practiced, base on if it is a numerical, originally from an analog signal, or a variable of Boolean, originally from a digital signal.

-          Variable of Numerical: is changed to a value of engineering base on a look up table, or a linear regression, etc… Conversion of Signal to Engineering. Another joint DB variable is issued.

-          Variable of Boolean: here the value of Boolean can be reversed or not, base on the logic the developer desires to use in the core application. For instance, so as to have fail-safe logic, the device status could be notified by a signal of “0V”, which is more suitable for encoding a “TRUE”. Another joint DB variable is issued.

The variable goes through a layer of “Forcing”, where its value can be strengthen by the user for maintenance or commissioning purposes. The variable is issued by the input interface of hardware.

- The variable is transferred systematically to the “States Variables” CODAC Interface transmission mechanism and can be employed by the core application of PLC.