Programmable controller with building blocks having modules that can be combined into a single unit

A PLC of building block type comprising:

• a switch module incorporating a switch part having N-to-N switch function between serial communication lines with a plurality of lines;
• and
• a plurality of device modules individually incorporating device systems with various function device module characteristics;
• wherein a CPU system having CPU functions of said PLC is incorporated either in said switch module or in a CPU module that is provided independently of said switch module;
• wherein said plurality of device modules and the switch module incorporating said CPU system, or said CPU module, said plurality of device modules and the switch module not incorporating said CPU system, are connected together into a single body in a building block structure through module-connecting mechanisms;
• and
• wherein dedicated serial communication lines each with a single line or a plurality of lines connect between said switch module incorporating said CPU system and each of said plurality of device modules such that a star-shaped serial communication network is formed with said switch module incorporating said CPU system as a central node and each of said plurality of device modules as a peripheral node, or between said switch module not incorporating said CPU system and said CPU system and each of said plurality of device modules such that a star-shaped serial communication network is formed with said switch module not incorporating said CPU system as a central node and said CPU system and each of said plurality of device modules as a peripheral node;
• wherein each of said module-connecting mechanism comprises a first connecting mechanism on the side of said switch module and a second connecting mechanism on said CPU module or one of said plurality of device modules;
• wherein said first connecting mechanism comprises:
• a connector half on the side of said switch module that is provided on one of side surfaces of module housing of said switch module and has a communication terminal groups for a plurality of lines;
• and
• switch connection lines that connect each of said communication terminal groups of said connector half on the side of said switch module and a corresponding one of communication ports of said switch part inside said switch module,
• wherein said second connecting mechanism comprises:
• a near connector half on said CPU module or one of said plurality of device modules that is provided on a side surface of module housing of the corresponding module on the side nearer said switch module when the modules are connected together and has one or more communication terminal groups corresponding to the number of lines of serial communication lines introduced from another module adjacent on the nearer side;
• a far connector half on said CPU module or one of said plurality of device modules that is provided on another side surface of said module housing of the corresponding module on the side farther from said switch module when the modules are connected together and has one or more communication terminal groups corresponding to the number of lines of serial communication lines introduced from another module adjacent on the farther side;
• inner system connection lines connecting one or more of said communication terminal groups of said near connector half that are assigned to the corresponding module and a communication interface incorporated in the corresponding module;
• and
• inner connector connection lines connecting remaining ones of said communication terminal groups of said near connector half excluding said one or more assigned communication terminal groups and the communication terminal groups of said far connector half.