When the PLC was invented, designers found a way to use the existing knowledge of the Relay Control System designers for programming the PLC. Another reason is that the PLC programmers usually prefer to define the actions in terms of contacts, which again was the most commonly used control sys...
For this reason, a separate manual was prepared for the CP 521 BASIC module. This manual was designed to provide only information and examples pertinent to the CP 521 BASIC module yet still satisfy the increasing demands placed on technical documentation. These include: • The standardization of...