This paper presents about the Cyclic Redundancy Check – 16, a generator polynomial for error detection, which is normally used in MODBUS Remote Terminal Unit. It starts with explaining the noise phenomena that are often generated into a useful signal when it is transmitted through a noisy channel. Some types of error which usually affects bits of a transmitted data bytes are introduced. The complete method for designing a good generator polynomial for detecting the error is then presented. Next, Cyclic Redundancy Check -16 as an example of generator polynimial is discussed. The explanation includes method for software implementation of the CRC. Two methods are introduced which are loop – driven method and table - driven method. Finally, ...