SLAVE UNITS AND NETWORK SYSTEM AS WELL AS SLAVE UNIT PROCESSING METHOD AND DEVICE INFORMATION COLLECTING METHOD

A network system is constructed by connecting a safety PLC constituting a master unit and safety slaves 2 to each other through a safety network 3. The safety slaves each have a device information storage unit 25 for storing individual information and status information of the safety devices connected. The individual information is acquired and stored in advance, while the stored contents of the status information are updated based on the result of monitoring the status of the safety devices in operation. These processes are executed by a MPU 23. In response to a request from the safety PLC, the device information stored are transmitted, so that the safety PLC can collect and manage the device state as well as the normal state of the slave units.