CC-Link

What Is CC-Link?

CC-Link is a fieldbus network developed by Mitsubishi Electric Corporation. Connecting robot controllers and large numbers of solenoid valves normally requires extensive wiring, but CC-Link allows connection with just 4 cables, dramatically reducing wiring work.

CC-Link is especially effective for connecting robot controllers. Standard I/O wiring requires many individual wires, but CC-Link completes the connection by passing just 4 dedicated cables. When additional CC-Link devices are present, simply continuing the cable to the next device completes the wiring.

CC-Link Wiring

The following uses the Q series CC-Link unit "QJ61BT11N" as an example. CC-Link always consists of a master station and local stations (slave stations). The PLC acts as the master station.

Connect each unit with CC-Link cables, and always attach terminating resistors at both ends of the connection. Terminating resistors are included with CC-Link devices. Remote I/O units are input/output units compatible with CC-Link, so no separate I/O units are required.

CC-Link Configuration

Understanding the following concepts is important when configuring CC-Link.

A station number is an address that identifies each device on the network. The master station is assigned station number 0; local stations are assigned numbers 1 and above. Duplicate station numbers prevent a device from joining the network, so each device must have a unique number.

Occupied station count is the setting for how many station numbers to allocate to one local device. A higher occupied station count provides more functionality, but since the CC-Link station number limit is 64, fewer total devices can be connected. Check each device's manual to determine the occupied station count.

Actual Configuration Workflow

First, physically connect the devices together with CC-Link cables. When multiple devices are present, connect them in a chain: master (PLC) → Device 1 → Device 2. Then attach the included terminating resistors at the very beginning and very end of the connection.

After connecting, set the CC-Link communication speed. Local devices typically have their own speed settings — set all of them to the same value. Using the maximum speed supported by all devices is recommended. For example, if all connected devices support up to 10 Mbps, set 10 Mbps. If even one device supports only up to 5 Mbps, set 5 Mbps for all.

*Note: With very long cables or many relay points, reducing the speed may be necessary to avoid communication errors.

Configuration methods vary by device: some units have physical rotary switches on the front panel, while others are configured via computer connection. The "QJ61BT11N" uses rotary switches on the front panel. Set the station number to 0 to designate it as the master station using the STATION NO switch.

The communication speed is set using the "MODE" rotary switch (the red one shown above). For reference, 10 Mbps corresponds to position 4.

Configuring station numbers and other settings may seem complex at first, but once you have done it once it becomes clear. Start by confirming the station type, occupied station count, and CC-Link version for each device. The "QJ61BT11N" supports both Version 1 and Version 2. Versions 1 and 2 can coexist on the same network, so there is no need to worry about that detail. The version for each device is fixed by the device itself; refer to each device's manual. If even one device on the connected network is Version 2, configure the master as Version 2. Additionally, some devices change their occupied station count depending on the features used. For IAI controllers, half direct-value control occupies 2 stations, while full direct-value control occupies 4 stations. This is configured in advance in the IAI controller's parameters; the occupied station count is then determined by that setting. Station type is also fixed by the device. I/O terminal blocks are Remote I/O stations — stations that use only bit devices and do not require word devices. IAI controllers, which also use word devices, are Remote Device stations. Devices with a CPU such as a PLC are Intelligent Device stations. However, there is no need to memorize all of this — it is documented in each device's manual, so configure according to the manual. For occupied station counts, you can also call the device manufacturer's support center; they will tell you based on what features you need to use. This information is also in the manual.

The key point is that the occupied station count, version, etc. are not set freely by the master (PLC side) — they are determined by how the local device is used, and the PLC side simply registers the connected device's information. The same applies to the local station side. Local stations do not have an item for setting occupied station count (Intelligent Device stations are an exception). Local station settings typically consist only of station number and communication speed. Once you configure the local station's device parameters and determine how it will be used, the occupied station count, version, and scaling factor are determined automatically. Understand that occupied station count and version are not set by the PLC side — they are automatically determined by the device's functionality.

Once each local station's device settings are complete, assign the station numbers. The order in which station numbers are assigned does not matter — it does not need to match the physical CC-Link connection order. Assign them in any order you prefer.

Device 1:
Remote Device station, Ver.1
2 stations occupied

Device 2:
Remote Device station, Ver.1
2 stations occupied

In GX Works2, open the navigation panel and go to "Parameter" → "Network Parameter" → "CC-Link."

Enter the number of units and configure the device numbers for Remote Input (RX) and Remote Output (RY). Use larger numbers such as X400 and Y400 to avoid overlapping with standard I/O numbers.

Configure the remote registers in the same way. Assign a number such as "W100" for RWr and "W200" for RWw to make them easy to distinguish. RWr is data received from local stations (read-only); RWw is data sent to local stations (write-only).

When configuring CC-Link for the first time, it is strongly recommended to configure one unit at a time. Configuring all units at once makes it difficult to identify the cause when a device number assignment is off.

After configuring, always verify the assignment using the "Device Usage List." Devices with an asterisk (*) in the parameter column are areas assigned by CC-Link.

Device 1 assignment example:
Input devices: X400 to X43F
Output devices: Y400 to Y43F
Input word devices: W100 to W107
Output word devices: W200 to W207

Next, configure Device 2.

How to Verify Device Assignment

GX Works2 includes a convenient feature that displays the device assignment status in a list. Go to menu bar "View" → "Docking Window" → "Device Assignment Check."

A separate window opens. Enter the "First I/O No." in the upper left to view the assignment status of that unit in a list.

FAQ