A programmable logic controller (10) is connected to external equipment (40) through a serial communication unit (30), and the programmable logic controller (10) includes: a memory (7), including a user program (11) and a setting document (13), where the user program (11) records both of a command for the communication interface device and command target information thereof, and the setting document (13) saves address information corresponding to the command target information; and a processor (8), reading the user program (11) and the setting document (13) to execute the command.

A programmable logic controller (10) is connected to external equipment (40) through a serial communication unit (30), and the programmable logic controller (10) includes: a memory (7), including a user program (11) and a setting document (13), where the user program (11) records both of a command for the communication interface device and command target information thereof, and the setting document (13) saves address information corresponding to the command target information; and a processor (8), reading the user program (11) and the setting document (13) to execute the command.