According to the IEC standard, %MW represents a memory word register (for example, a language object of type memory word).
A programming unit that has 1 input and returns 1 immediate result. However, unlike FBs, it is directly called with its name (as opposed to through an instance), has no persistent state from one call to the next and can be used as an operand in other programming expressions.
Examples: boolean (AND) operators, calculations, conversions (BYTE_TO_INT)
A programming unit that has 1 or more inputs and returns 1 or more outputs. FBs are called through an instance (function block copy with dedicated name and variables) and each instance has a persistent state (outputs and internal variables) from 1 call to the other.
Examples: timers, counters
(least significant bit/byte) The part of a number, address, or field that is written as the right-most single value in conventional hexadecimal or binary notation.
(most significant bit/byte The part of a number, address, or field that is written as the left-most single value in conventional hexadecimal or binary notation.
(proportional, integral, derivative) A generic control loop feedback mechanism (controller) widely used in industrial control systems.
(pulse width modulation) A fast output that oscillates between off and on in an adjustable duty cycle, producing a rectangular wave form (though you can adjust it to produce a square wave).
