Beckhoff CX8110 Embedded PC: A Complete Guide from Hardware Architecture to Distributed Clock and Persistent Data Protection

In the field of industrial automation, embedded controllers need to have compact size, high reliability, and flexible fieldbus capabilities. Beckhoff's CX8110 embedded PC is based on Arm ®  Cortex ®- The A9 processor (800 MHz) integrates EtherCAT slave interface, 1-second UPS persistent data storage, and Windows Embedded Compact 7 operating system, making it a cost-effective controller designed specifically for distributed control and slave applications. Its width is only 71 mm, which can be directly installed on a DIN rail and connected to Beckhoff Bus Terminals (K-bus) or EtherCAT Terminals (E-bus) through the power terminal on the right side. CX8110 can function as an EtherCAT slave and continue to run control programs locally in the event of communication interruption with higher-level master stations. This article will comprehensively analyze the system composition, installation and cooling, power and grounding, network and bus interfaces, distributed clock configuration, 1-second UPS persistent variable mechanism, DIP switch explicit device identification, diagnosis, and maintenance points of CX8110 from the perspective of engineering applications, providing a detailed technical reference for on-site engineers.

Product Overview and Core Features

The CX8110 belongs to the Beckhoff CX8100 series, and its basic configuration includes:

Processor: Arm Cortex-A9 single core, 800 MHz

Memory: 512 MB DDR3 RAM (non expandable)

Storage: 512 MB microSD card (SLC industrial grade, upgradable to 16 GB)

Interface: 1 x Ethernet port (X001, 10/100 Mbit/s, used for programming and configuration), 2 x EtherCAT slave interfaces (X101 input, X102 output)

Bus interface: automatically recognizes K-bus (bus terminal) or E-bus (EtherCAT terminal)

1-second UPS: Built in UltraCap capacitor, can save up to 1 MB of persistent data to a microSD card after power failure

Real time clock: battery backup (CR2032)

Working temperature: -25 ° C~+60 ° C (horizontal installation), reduced to 50 ° C when vertical or non ideal direction

Typical application scenarios for CX8110 include:

As an EtherCAT slave, execute local PLC programs (IEC 61131-3)

Independently operate critical control logic in case of higher-level main station failure

Expand fieldbus through EtherCAT terminals (such as PROFIBUS, CANopen, PROFINET)

Cooperate with distributed clock (DC) to achieve high-precision synchronization

Mechanical installation and heat dissipation requirements

2.1 Size and Weight

Width x Height x Depth: 71 mm x 100 mm x 73 mm

Weight: Approximately 230 grams

2.2 Installation direction and ventilation gap

The top and bottom of the CX8110 casing are equipped with ventilation holes. To ensure stable operation of the CPU at an ambient temperature of 60 ° C, it must be installed horizontally (with the interface facing the side and the ventilation holes vertically up and down). At this time, at least 30mm of free space should be reserved above and below the device.

Permitted vertical installation: If the control cabinet space is limited, the CX8110 can be installed vertically (with the interface facing up or down), but the upper limit of the ambient temperature should be reduced to 50 ° C. Regardless of the direction, the connected bus terminals must also support this installation direction.

Prohibited installation method: Do not place the equipment on the side (with ventilation holes blocked), otherwise it may cause overheating.

2.3 DIN rail installation steps

Push the CX8110 onto the TS35/7.5 or TS35/15 rail (compliant with DIN EN 60715) from the front.

After hearing the "click" sound, use a screwdriver to push down the left locking buckle to fully engage with the guide rail.

Check if the equipment is secure.

When disassembling, first disconnect the power supply, then use a screwdriver to lift the left locking buckle and remove the device from the guide rail.

Power connection and grounding

3.1 Power Supply Requirements

CX8110 is connected to 24 V DC through the spring terminal on the right power terminal. The terminal block provides two sets of power supplies:

Us (upper row 24V/0V): Provides power for CPU module and bus communication (K-bus or E-bus).

Up (bottom row+/-/±): Provides power to the bus terminals and connected sensors/actuators through power contacts.

Power requirements:

Rated voltage: 24 V DC (allowable range -15%/+20%, approximately 20.4 V~28.8 V)

Minimum power supply capacity: 4 A (ensuring full load operation)

Wire cross-section: 0.5~2.5 mm ² (AWG 20~14), wire stripping length 8~9 mm

Terminal power supply current on the bus: maximum 2 A (internal current limit)

UL compliance requirements (equipment has obtained UL certification):

It must be powered by a 24 V power supply that complies with NEC Class 2, or an isolated power supply protected by a maximum 4 A fuse (UL 248).

Class 2 power supplies shall not be connected in series or parallel with other Class 2 power supplies.

3.2 Grounding and PELV specifications

The wiring inside the control cabinet must comply with EN 60204-1:2006 (PELV):

The 0 V of the power supply and the protective earth (PE) must be at the same potential (connected inside the control cabinet).

One side of the circuit (or a point of the power supply) must be connected to the protective grounding system.

Important operating rules:

When disconnecting the power supply, first disconnect the 24V line and then disconnect the 0V line, otherwise a current loop may be formed through the shielding layer.

The connected peripherals (such as the control panel) must have the same PE and 0 V potential as the CX8110, otherwise it may damage the device.

3.3 Power LED indicator light

Us 24V (green): CPU module and bus communication power supply are normal

Up 24V (green): The power contacts are supplying power normally

K-BUS RUN (green, only K-bus mode): Communication is normal

K-BUS ERR (flashing red): K-bus error (see diagnostic section for details)

L/A (green, only in E-bus mode): off=not connected; Always on=Connected with no data; Flashing=data transmission and reception

Interface Explanation

4.1 Ethernet interface X001

10/100 Mbit/s RJ45 port, used for device programming, configuration, and ADS communication. DHCP is enabled at the factory and can automatically obtain an IP address; It can also be set as a static IP in the operating system. The LED indicates:

Up LED (LINK/ACT): green constant light=connected, flashing=data transmission and reception

LED (SPEED): Orange=100 Mbit/s, Off=10 Mbit/s

The maximum cable length is 100 meters (CAT5). Supports all TCP/UDP based non real time protocols.

4.2 EtherCAT Slave Interface X101 (Input) and X102 (Output)

Speed: 100 Mbit/s

Maximum input/output data length: 480 bytes each (up to 256 variables)

Data alignment requirements for ARM processors: As Arm Cortex-A9 processors require aligned access, attention must be paid to the following when creating process data:

WORD (2 bytes) must be located at even address offset

DWORD/DINT/REAL (4 bytes) must be located at an address offset that can be divided by 4

It is recommended to use dummy variables or rearrange structure members to ensure consistent data structure length on x86 and Arm systems. Otherwise, it may cause the controller to crash.

4.3 microSD card slot

Located under the front cover, the factory comes standard with a 512 MB industrial grade SLC card. You can choose a 16 GB card (order number CX1900-0132). Replacing the storage card must be done in a power-off state. The recommended replacement cycle for CF cards/storage media is 10 years.

4.4 Reset button and configuration mode

Long press the reset button (located on the front of the device) and start the device at the same time to put the CX8110 into Config mode (ERR LED turns red first and then yellow). This mode is used to download new firmware or repair PLC programs that cannot be started.

4.5 DIP switch (S101) and explicit device recognition

CX8110 provides 10 DIP switches (switches 1-8 are available, switches 9-10 are reserved). The Explicit Device Identification value (0-255) can be set through a combination of switches to uniquely identify the slave station in the EtherCAT network. This allows for hot replacement of CX8110 at runtime without the need to reconfigure the main station.

Example setting: To set the value 67, turn DIP 1, 2, and 7 to ON (2 ⁰+2 ¹+2 ⁶=67). In TwinCAT, the "Using Dipswitch Value" option needs to be enabled first (see the configuration section below).

Software and Operating System

CX8110 comes pre installed with Microsoft Windows Embedded Compact 7. Attention: The support period for this operating system has ended and security updates are no longer available. TwinCAT only supports up to Build 4024.

In the factory state, CERHOST (remote display) and TELNET services are disabled. To enable it, you need to use a card reader to delete the CeRemoteDisplay_Sisable.reg and Telnet_Sisable.reg files in the RegFiles folder of the microSD card, and then restart the device.

5.1 FTP Server and Firewall

Starting from the mirrored version CX8100_WEC7_LF_v604h-TC31-B4022.20, the firewall is enabled by default and passive FTP connections (such as Microsoft clients) will be blocked. It is recommended to use active FTP mode and open TCP ports 20 and 21 in the firewall.

5.2 Web Services and Beckhoff Device Manager

CX8110 can be remotely configured through a browser:

Old image: HTTP port 80

New image: HTTPS port 443

Example of Access Address: https://169.254.136.237/config or https://CX ‑16C2B8/config

Default username: Administrator, password: 1

Remote Display can be enabled in Device Manager, and then the CERHOST tool (cerhost. exe) can be used for remote desktop operations.

TwinCAT project configuration process

6.1 Connecting to CX8110

Create a new XAE project in TwinCAT 3.

Click on SYSTEM → Choose Target → Search (Ethernet).

Enter the IP address or hostname of CX8110 (the hostname is composed of CX+MAC address followed by 3 bytes by default, such as CX aabbcc).

Add route, enter username (Administrator) and password (1).

Select the target system and confirm.

6.2 Scanning I/O devices

After connection, right-click on I/O → Devices → Scan. According to the actual type of bus connected, the system will discover K-bus interface (bus terminal) or EtherCAT interface (EtherCAT terminal). After confirming the scan, all terminals will appear in the tree view.

6.3 Creating Process Data (Pay Attention to Alignment)

Due to the alignment requirements of Arm processors, when creating input/output variables:

Create a data structure using Create Array Type and check if SIZEOF matches expectations.

If the length of the structure is different on x86 and Arm, dummy bytes should be added to force alignment.

6.4 Creating a PLC Project

Add a standard PLC project, write a simple program and build it. Then associate PLC variables with hardware I/O through Attach Variables. Finally, click on Activate Configuration and switch TwinCAT to Run mode.

6.5 Explicit Device Identification (DIP Switch) Settings

Click on the EtherCAT slave (CX8110) in the TwinCAT tree view, and in the EtherCAT Slave tab:

Check 'Using Dipswitch Value'

Alternatively, cancel this option and enter a numerical value directly in the Value field below (overriding DIP switches).

Distributed Clock (DC) Configuration

CX8110 supports distributed clocks and can be used as a slave to synchronize with the upper level master. Configuration is divided into two steps:

7.1 Enable DC on CX8110 (slave) side

Click on the EtherCAT slave of CX8110 in TwinCAT.

Check Enable Synchronization in the EtherCAT Slave tab.

After confirmation, DcToTcTimeOffset, DcTimeDiff, and DcState variables will appear under InfoData.

Click on the EtherCAT master (lower level master) of CX8110 and enable DC Time controlled by CCAT Time (Master Mode) in EtherCAT → Advanced Settings.

7.2 Configuring DC on the upper master station side

Connect CX8110 to the upper level master station (such as another Beckhoff controller).

Scan CX8110 in the TwinCAT project on the main site.

Click on the CX8110 slave station, switch to the DC tab, and select DC Synchron.

Ensure that the synchronization task cycle is ≤ 5 ms and the CPU load is below 60%. The best synchronization effect can be achieved with a period of 1-2 ms.

Diagnostic variables:

DcTimeDiff (DINT): master-slave clock deviation, in ns. Under a task cycle of 1 ms, a deviation of<10 ns is optimal, and<100 ns is acceptable.

DcState: A value of 0x_2 indicates that TwinCAT time is controlled by CCAT time.

Note: If only K-bus terminals (non EtherCAT) are used, the distributed clock function has no practical significance.

1-second UPS and persistent variable protection

The CX8110 is equipped with a capacitive 1-second UPS, which can provide brief power to the CPU after the main power supply is cut off, to save persistent variables (PERSISTENT) to the microSD card. The maximum amount of data that can be reliably saved throughout the entire lifespan is 1 MB.

8.1 Working principle and configuration

Declare the variable that needs to be retained during power outage as VAR PERSISTENT in the PLC.

Loop the function block FB_S-UPS_CX81xx (located in the Tc_2SUPS library) in the fastest task.

Set eUpsMod:

ESUPs_WrPersistData_Shutdown (default): Automatically shuts down quickly after saving data

ESUPs_WrPersistData_CoShutdown: Only saves data, does not shut down

ESUP_SimediateShutdown: Immediately shut down (without saving data)

ESUPS-CheckPowerStatus: Only detects power status

Persistent data is saved in WinCAT 3.1 Boot Port_85x.bootdata. When the system starts, the file will be loaded and a backup *. bootdata old will be created.

8.2 Precautions

Only TwinCAT can control the 1-second UPS, and other applications must not interfere.

1 second UPS does not supply power to K-bus/E-bus, so bus data may become invalid after UPS activation.

After power failure detection, other application logic should be stopped from being called:

iecst

IF NOT FB_S_UPS_CX81xx.bPowerFailDetect THEN

//Normal procedure

END_IF

If persistent data loading fails (backup is being used), it can be determined through PlcAppSystemInfo. OldBootData (True indicates backup is being used). To force the deletion of invalid backups, you can set the registry:

[HKEY_LOCAL_MACHINESOFTWAREBeckhoffTwinCATPLC] "ClearInvalidPersistentData"=dword:00000001

Or check Clear Invalid Persistent Data in TwinCAT.

8.3 Real time clock (RTC) slow running problem

If the system time of CX8110 is found to be slow, the reason is that the TwinCAT real-time driver failed to update the operating system clock in a timely manner under high load or long cycle tasks. Solution: Modify the registry

[HKEY_LOCAL_MACHINEPlatform] "SoftRTC"=dword:0

Force hardware RTC to be read every time Windows time is requested (which will increase slight CPU load).

Diagnosis and troubleshooting

9.1 Overview of LED indicator lights

Meaning of LED color/status

TC Green TwinCAT Run Mode

TC Red TwinCAT Stop Mode

TC Blue TwinCAT Config Mode

EC RUN green constant light EtherCAT OP status

EC RUN green flashing (200ms) PRE-OP status

EC RUN green flashing (200ms on/1000ms off) SAFE-OP status

EC ERR red constant light EtherCAT not configured or incorrect

K-BUS ERR flashing red K-bus error (see below)

9.2 K-bus Error Diagnosis

When the red K-BUS ERR LED flashes in a specific sequence, the fault can be located by counting the flash (start flag), slow flash count (error code), and second slow flash count (error parameter):

Error code parameter description and solution

3 slow flashes of 0 K-bus command error, failure to insert terminal or damage to one terminal; Using the split method to troubleshoot faulty terminals

Check if the bus terminal (KL9010/EL9010) is installed after 4 slow flashes of the 0 power module and disconnection

Check if terminal n+1 is correctly connected after 4 slow flashes of terminal n and subsequent disconnection

5 slow flashing n register communication errors, replace the terminal at position n

7 slow flashes, 0 process data length mismatch check for consistency between configuration and actual terminals

In TwinCAT, the K-bus state variable is located under the bus coupler. If the value ≠ 0, check the corresponding bit (bit0=error, bit1=configuration change, etc.). The recommended K-bus task cycle is ≤ 50 ms, and the actual update time is 1-5 ms.

9.3 Quick search for common problems

Possible causes and solutions for the fault phenomenon

Unable to connect via Ethernet due to IP address conflicts, firewall blocking DHCP/static IP checks; confirm port 80/443 is open

Remote display without screen CERHOST not enabled. Delete disabled registry file according to section 6.1 and restart

Persistent data not recovered, UPS not enabled, write filter blocking check if 1-second UPS is enabled in BIOS (CX8110 has no BIOS, automatically enabled); FBWF exceptions must include Boot

EtherCAT slave does not enter OP slave address conflict, process data alignment error check explicit device identification value; Confirm that all variable alignment meets Arm requirements

RTC time reset battery depleted, replace CR2032 battery (positive pole to the left, facing Ethernet port)

Maintenance and retirement

10.1 Regular replacement of components

Recommended replacement cycle for components

Motherboard battery (CR2032) 5 years

MicroSD card for 10 years

1 second UPS capacitor has the same lifespan as the equipment (no need to replace)

When replacing the battery, open the front cover and use a plastic screwdriver to pry out the old battery from the battery compartment, then push in the new battery (with the positive pole pointing to the left, i.e. towards the Ethernet port).

10.2 Cleaning and ESD protection

The power must be disconnected before cleaning. Only use a soft damp cloth to wipe the outer shell, and the ventilation duct can be cleaned with a vacuum cleaner. Prohibit the use of compressed air.

Avoid corrosive cleaning agents, solvents, abrasives, or hard objects.

ESD protection measures (grounding wristbands, conductive pads, etc.) should be taken when replacing internal components.

10.3 Retirement and Disposal

After disconnecting the power, remove the device from the DIN rail. MicroSD cards should be physically destroyed to prevent data leakage. Electronic components shall be disposed of in accordance with national regulations on electronic waste.

Summary of Technical Specifications

Project specifications

Processor Arm Cortex-A9 800 MHz

Memory 512 MB DDR3 RAM

Storage microSD 512 MB (expandable up to 16 GB)

Interface 1 x 10/100 Ethernet, 2 x EtherCAT slave stations

Bus K-bus/E-bus automatic recognition

1 second UPS support, up to 1 MB of persistent data can be saved

Power supply 24 V DC (-15%/+20%), maximum power consumption 9 W (including UPS charging)

Working temperature -25 ° C~+60 ° C (horizontal), -25 ° C~+50 ° C (vertical)

Protection level IP20

Certified CE, UL

Operating system Windows Embedded Compact 7 (support has expired)

TwinCAT 3.1， Separate authorization is required