Patent ID: 6880029

Claim:
A programmable controller comprising: an I/O unit for input and output with various pieces of equipment that are to be controlled; an I/O memory for storing I/O data corresponding to the I/O unit; a user program memory for storing user program corresponding to user defined control requirements; a system program memory for storing various system programs in order to realize functions as a PLC (lower level programmable controller); a microprocessor for executing system program stored in the system program memory; and an interruption trigger generating means for generating an interruption trigger at a prescribed constant interval; said system program at least comprising; a user program execution process for executing user programs stored in the user program memory; an I/O refresh process for refreshing I/O data between the I/O memory and the I/O unit; and a peripheral service process comprising data communication with an upper-level computer, communication with special I/O or remote I/O, and data relay process in a factory automation (FA) network, wherein: the user program execution process and I/O refresh process are executed by a normal process of the microprocessor for a first prescribed constant amount of time, and the peripheral service process is executed for a second prescribed constant amount of time according to an interruption process of the microprocessor every time an interruption trigger is generated by the interruption trigger generating means, and wherein the first prescribed constant amount of time and the prescribed constant second period of time are unequal in duration.