In the fields of modern high-speed packaging, printing, assembly, and pharmaceutical machinery, the requirements for control systems have long exceeded simple logical sequence control. The real challenge lies in how to achieve high synchronization of dozens of servo axes, precise electronic cam tracking, fast flying shear, and complex trajectory interpolation, while ensuring absolute reliability of the system in harsh industrial environments. The PacDrive series controllers of ELAU (now owned by Schneider Electric) were born for this purpose, and the C600 model, as a powerful platform based on Intel processors and VxWorks real-time operating system, still plays a core role in a large number of high-end devices today.
For engineers responsible for system integration, upgrading, or daily maintenance, a deep understanding of the technical details, wiring specifications, communication configuration, and diagnostic methods of the C600 controller is key to ensuring efficient and stable operation of the equipment. This article will extract a complete application guide for engineering practice based on the official technical data manual.
Core hardware and real-time operating system: laying the foundation for high performance
The design philosophy of the PacDrive C600 controller is to integrate the reliability of PLC with the computing power of PC, while eliminating the non deterministic latency of general-purpose operating systems.
1. Processor and Memory
CPU: Intel Pentium M 1.6 GHz processor, equipped with 1 MB of L2 cache. This processor was a low-power, high-performance embedded choice at the time, capable of handling complex kinematic calculations and a large number of PLC logic operations.
RAM: 256 MB system memory, used to run real-time operating systems and user programs.
NVRAM: 256 kB non-volatile RAM used to maintain critical process variables and diagnostic data after power failure.
Storage medium: CompactFlash ™ Card (at least 128 MB), used to store operating system firmware, user applications, and recipe data. The replaceability of CF cards greatly facilitates on-site system recovery and upgrades.
2. Real time operating system: VxWorks
Unlike soft PLCs based on Windows or Linux, the C600 uses Wind River's VxWorks real-time operating system. VxWorks is renowned in the fields of aerospace, defense, and industrial automation for its deterministic task scheduling, extremely low interrupt latency, and high long-term stability. This means that even in the worst-case scenario, the C600 can ensure that tasks are completed within the specified deadline, which is a prerequisite for achieving a fast task cycle of 250 µ s and a typical I/O response time of 500 µ s.
3. Diagnosis and status display
The front panel of the controller is equipped with an alphanumeric diagnostic display screen and multiple status LEDs (power, operation, error, bus status, etc.). This hardware diagnostic function is particularly valuable when the system starts or malfunctions, as it can quickly determine the controller status without connecting programming software.
Motion Control Core: SERCOS Bus and Servo Axis Management
The motion control capability of C600 comes from its integrated SERCOS (Serial Real time Communication System) interface, which was one of the most advanced high-speed real-time servo buses at the time.
1. SERCOS interface specifications
Interface: Two fiber optic ports (X14, X15) with a communication rate of up to 16 MBaud.
Slave capacity: Up to 99 SERCOS slaves can be connected, with typical slaves including ELAU MC-4 servo drives, SCL intelligent drives, and iSH series servo motors.
Synchronization performance: Supports precise synchronization under all SERCOS cycle times, and can run up to 255 parallel motion curves simultaneously.
2. Motion control function
The motion control kernel based on VxWorks can generate and coordinate the following functions:
Point-to-point positioning
Electronic Gear
Electronic Cam, supporting up to 256 Cam Switch Groups
Flying Shear
Interpolation motion (linear, circular)
Virtual Master Encoder function
For applications that require high-precision position capture, the C600 provides 16 Touchprobe inputs with a resolution of up to 10 µ s (when the bus cycle is 1, 2, or 4 ms), making it ideal for capturing axis positions in high-speed motion for measurement or quality inspection.

Rich communication interfaces: connecting everything
The C600 is designed as an information hub on the production line, integrating multiple fieldbus and Ethernet communication interfaces in addition to the motion bus.
1. Fieldbus interface
PROFIBUS DP (X20): Master/Slave configurable, up to 12 MBaud, using standard DB9 interface. Through PROFIBUS, C600 can connect remote I/O, frequency converters, HMI and other devices, supporting up to 126 stations, with I/O data up to 3584 bytes input/output.
CAN/CANopen (X19): Supports CAN 2.0A and CANopen protocols, used to connect relatively simple sensors, encoders, or specialized modules.
DeviceNet: It needs to be connected through an adapter cable and supports slave mode.
EtherNet/IP: Optional hardware module is required, supporting either Scanner or Adapter modes.
2. PacNet high-speed I/O bus (X12, X13)
PacNet is ELAU's proprietary high-speed expansion bus used to connect distributed I/O modules. Through PacNet, up to 128 digital inputs, 128 digital outputs, and 128 Touchprobe inputs can be expanded. This is crucial for applications that require a large amount of high-speed signal acquisition.
3. Ethernet (X10)
Provide standard 10/100 Base-T Ethernet interface (RJ45). Based on the TCP/IP protocol stack, it supports the following functions:
OPC Server: Provides OPC DA interface that seamlessly integrates with SCADA or HMI software on any Windows platform (such as Intellution iFix, Siemens WinCC).
Web server: allows remote monitoring of controller status, variables, and diagnostic information through a standard browser.
FTP server: facilitates remote uploading/downloading of program files, recipe data, and logs.
SMTP: Supports sending alerts and event notifications via email.
4. Serial interface
COM1 (X17): RS232, It can be used to connect serial HMI panels, barcode scanners or Modbus RTU devices.
COM2 (X18): RS485, Support multi station Modbus RTU communication or connection to smart meters.
5. Main encoder interface (X11)
This interface is used to connect an external spindle encoder and achieve tracking of the spindle's motion. Supports two types:
SinCos absolute value encoder: 1 Vpp sine/cosine signal, with reference signal and RS485 parameter channel (for reading absolute position).
Incremental encoder: supports A, B, O (zero position) differential signals.
Important Warning: The manual clearly warns that the main encoder plug must be plugged in and out while the controller is powered off, otherwise it may cause hardware damage.
Onboard I/O: meets basic control requirements
For small applications or situations that do not require remote I/O, the C600 integrates a considerable number of native I/O points, reducing the cost and space of additional modules.
1. Digital input (X3)
Quantity: 20 points, compliant with IEC 61131-2 Type 1 specification.
Electrical characteristics: High level effective (DC 20-33V is logic "1", 0-6V is logic "0"), typical input current value is 5mA @ 24V.
Filtering: Parameterized selection of 1 ms or 5 ms input filtering to eliminate contact jitter.
2. Digital output (X2)
Quantity: 16:00.
Electrical characteristics: The output high level is (UL-3V) to UL (UL is the externally supplied logic voltage, connected to pin 3 of X1), the rated current is 250 mA/channel, and the surge current can reach 2 A for 1 second. The output has short-circuit protection.
Transmission delay: Typical value of 100 µ s, suitable for high-speed switch signals.
3. Interrupt input (X4)
Quantity: 4 points (shared some pins with Touchprobe input, but logically independent).
Function: Can be configured as an event triggered interrupt, used for signal processing with extremely strict time requirements (such as emergency stop, position capture trigger, etc.).
4. Touchprobe input (X4)
Quantity: 16:00 (T.00-T.15).
Resolution: 100 µ s; when the SERCOS cycle time is 1, 2, or 4 ms, the resolution can be increased to 10 µ s.
Typical application: When the rising edge of the photoelectric sensor is detected, the instruction position or actual position of the current axis is immediately locked for registration control, printing mark correction, etc.
5. Analog input (X5)
Quantity: 2 channels.
Range: Voltage mode: -10 V to+10 V; Current mode: -20 mA to+20 mA (to be selected through bridge connection J.0+or J.1+terminal).
Resolution: 12 bits (voltage 5 mV/LSB, current 5 µ A/LSB).
Input impedance: voltage 100 k Ω, current 500 Ω.
6. Analog output (X5)
Quantity: 2 channels.
Range: -10 V to+10 V.
Resolution: 12 bits (5 mV/LSB).
Load capacity: It is recommended to load>5 k Ω.
Auxiliary power supply: X5 also provides two 12V output voltages (12 V Out 0/1), which can be used to power external sensors.
7. Additional I/O Expansion
The maximum expandable digital/analog I/O capacity through PROFIBUS DP or PacNet bus is 3584 bytes each.

Requirements for power supply, environment, and mechanical installation
The design of C600 takes into account the actual conditions of industrial sites, but must comply with the following limitations to ensure long-term reliable operation.
1. Power specification (X1)
Main power supply: DC 24 V (-15%/+25%, i.e. 19.2 V to 30 V), maximum power consumption of the controller itself is 85 W (approximately 3.5 A).
External logic voltage (UL): provides driving power for digital output, also DC 24V, and needs to be separately connected to pin 3 of X1. This voltage is electrically isolated from the internal logic of the controller.
Watchdog Relay (WD): pins 7 and 8 of X1 are passive contact relay outputs. When the controller software is running normally and the watchdog is not triggered, the relay will close. If a serious malfunction or power outage occurs, the relay will release and can be used to drive external safety circuits.
UPS option: Internally available uninterruptible power supply (UPS), allowing for safe data storage and controlled shutdown in the event of an external 24V power outage. The maintenance cycle for UPS batteries is 3 years.
2. Environmental conditions
The environmental tolerance of C600 is classified according to IEC/EN 60721-3 standard:
Conditional operation (3K3) Transportation (2K3) Long term storage (1K4)
Environmental temperature+5 ° C...+45 ° C -25 ° C...+70 ° C -25 ° C...+55 ° C
Relative humidity 5%... 85% 5%... 95% 5%... 95%
Condensation, freezing, and water are prohibited
Attention: If UPS is selected, the upper limit of operating temperature is reduced to+40 ° C and the upper limit of storage temperature is reduced to+45 ° C.
3. Mechanical specifications
Dimensions: The packaging dimensions are 300 mm (depth) x 130 mm (width) x 400 mm (height), and the body weight is approximately 3.5 kg.
Protection level: The shell is IP20 and is only suitable for installation inside the control cabinet to prevent metal shavings, water droplets, etc. from entering.
Installation method: Fixed with standard DIN rails or bottom plate screws.
Programming and Engineering Software
The PacDrive C600 fully complies with the IEC 61131-3 international standard and supports all five programming languages:
Instruction List (IL)
Ladder diagram (LD)
Function Block Diagram (FBD)
Sequential Function Diagram (SFC)
Structured Text (ST)
And additional support for Continuous Function Diagram (CFC)
The engineering software is EPAS-4 (ELAU Programming and Automation System), which integrates PLC programming, motion parameter configuration, SERCOS bus debugging, HMI variable linking, and online monitoring functions. The software is built-in with:
8-channel software oscilloscope (Trace Recorder): resolution of 1 ms, capable of recording variable curves.
27 kB diagnostic data logger: Loop records system events and error messages.
OPC Server: Provides data access for third-party HMI.
For remote maintenance, the C600 has a built-in modem interface (requiring an external modem), which can be dial-up connected through a telephone line to achieve remote diagnosis, program download, and web access.
Key points of wiring and prevention of common errors
According to the connection table in the manual, the following wiring details are prone to errors and require special attention:
1. Power connection X1
Pin1 (DC 24V) and Pin3 (+UL) must be connected simultaneously, even if the digital output is not in use, the+UL should still be connected, otherwise some internal logic may not work properly.
If the current demand is high (such as driving multiple solenoid valves simultaneously), Pin1 and Pin2 can be used in parallel with Pin5 and Pin6 through external short circuiting, with a maximum current carrying capacity of 4A.
2. Polarity of digital input/output
All digital inputs and Touchprobe inputs are source type (PNP), meaning the common terminal is 0V and the signal terminal is connected to 24V effectively. Do not connect NPN type sensors, otherwise intermediate relays need to be added for conversion.
The digital output is also source type, and when the output terminal is conductive, it outputs 24V (relative to the common terminal 0V). Connect one end of the load to the output terminal and the other end to 0V.
3. Analog input wiring
Voltage measurement: directly connect AI+and AI -.
Current measurement: AI+and J.0+must be short circuited, and AI - must be connected back to A.GND. Otherwise, the correct reading cannot be obtained.
4. PROFIBUS DP bus (X20)
PROFIBUS specific connectors with terminal resistors must be used. The terminal resistors of the first and last nodes of the bus must be turned to the "ON" position, and the middle node must be turned to the "OFF" position.
The shielding layer must be grounded extensively at both ends and cannot be grounded solely through the DB9 casing.
5. PacNet bus (X12, X13)
Only ELAU certified dedicated PacNet cables are allowed to be used, and ordinary Ethernet cables should not be used as a substitute, otherwise it may cause communication failures or bus conflicts.
6. Real time clock battery
The controller has a real-time clock (RTC) battery inside, with a maintenance cycle of 5 years. After expiration, the service department should be contacted for replacement, otherwise the system time may be reset after power failure.
Troubleshooting and maintenance recommendations
1. Common fault phenomena and countermeasures
Possible cause investigation steps for the phenomenon
The controller cannot start, the display screen shows no indication that the 24V power supply is not connected or the voltage is too low. The Pin1-Pin2 voltage of X1 should be 20.4-30V. Check the external circuit breaker
Random shutdown during operation, watchdog relay releases CPU overheating, memory error, software abnormality to check if control cabinet temperature exceeds 45 ° C; reads diagnostic buffer through EPAS
SERCOS communication interruption, fiber optic damage, connector contamination, and inspection of fiber bending radius in case of substation power failure; Clean the connector; Check the status LED of MC-4 driver
Unstable PROFIBUS communication with incorrect terminal resistance settings, poor shielding, and address conflicts. Confirm that the terminal resistance of the first and last stations is ON. Check the grounding of the shielding layer; Scan bus address
The digital output point does not operate and the overload fuse is burnt out (internal electronic fuse), and the UL power supply is missing. Measure the X1 Pin3 voltage; Check if the output point is short circuited; Restart the controller to attempt recovery
2. Firmware and program upgrades
The operating system firmware can be upgraded through Ethernet or CF card. The firmware file needs to be placed in the root directory of the CF card and started according to specific steps.
Does CF card support hot swapping? The manual does not explicitly recommend that CF cards should usually be plugged in and out while the power is off to prevent file system damage.
3. Cleaning and Inspection
Regularly use low-pressure air to clean the cooling holes and internal fans (if any) of the controller to prevent dust accumulation and overheating.
Check if all connectors are securely locked, especially SERCOS fiber optic connectors, as looseness can cause communication errors.
