Programmable controller allowing an external peripheral device to monitor an internal operation state of a CPU unit

A programmable controller for controlling a control subject device such as an industrial apparatus based on a stored sequence program, comprising:

• a CPU unit containig a CPU;
• an interface having means for receiving a processing request from an external peripheral device through communication, and means for sending a processing response from the CPU unit to the external peripheral device;
• a CPU disposed in the CPU unit, for executing a sequence program and control programs that cause the CPU unit to operate;
• a sequence program storage unit for storing the sequence program;
• a control program storage unit for storing the control programs including a control program for measuring an internal operation state of the CPU unit;
• a data storage unit for storing data used in processing of the CPU;
• and
• an internal operation state storage unit for storing a measured internal operation state of the CPU unit,
• wherein the internal operation measuring control program enables the internal operation state of the CPU unit to be measured in response to a monitor processing request from the external peripheral device, and a measurement result to be sent to the external peripheral device, to thereby allow the external peripheral device to monitor the internal operation state of the CPU unit.