Connection Types

There are two types of messaging connections: I/O messaging connection and Explicit messaging connection.

I/O messaging connection includes the four methods explained below:

Connection Method	Description
Polling	First, a master device sends output data to a slave device and then the slave device responds. Data is normally exchanged in every communication cycle. The communication frequency can be changed by setting. This connection type is the most often used.
Strobe	First, a master device requests slave devices to send data with multicast messages, and then, each slave device responds individually. Data from many sensors on the system can be effectively gathered. When the master does not receive responses from all requested slave devices, a timeout error occurs.
Change Of State	A device sends data whenever it changes. Signals for device diagnosis are sent regularly in the background. This connection type is useful for remedying DeviceNet communication traffic.
Cyclic	A slave device transfers data regularly according to its internal timer. This connection type is typically used for communicating with a temperature Controller. The data transfer frequency is defined by master configuration.

KEY POINTS

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For Change of State and Cyclic, the ACK which verifies communication completion can be disabled by setting. However, never disable the ACK since communication errors cannot be detected.