ABB AC 800M Complete Guide

This means that in redundant configurations, all local I/O must be connected through fiber optic modules (such as TB807 and fiber optic expansion modules), and the electrical Modulus terminals are not available.

3.3 Common Reasons for Redundant Switching Failure

RCU Link cable fault: Use a multimeter to measure the resistance between terminals TB852/TB853, which should be less than 0.5 Ω normally. If there is interruption, replace cable TK851V010.

The firmware versions of the primary and backup CPUs are inconsistent: they must be exactly the same, including patch levels. Compare online through Control Builder.

Synchronization data timeout: If the application contains a large number of asynchronous variables (such as local clock), it can cause the backup CPU to be unable to complete state synchronization within the specified time. Solution: Place key data in the synchronized global data area.

Power supply fluctuation: Redundant CPUs have extremely high requirements for 24V power supply, with ripple not exceeding 5% (i.e.<1.2V pp). Use an oscilloscope to measure the CPU power terminal. If the ripple exceeds the standard, install an SD831 power filter.

Comprehensive analysis of communication interface module (CEX bus)

The CEX bus of AC 800M supports up to 12 communication modules, covering mainstream industrial protocols. The following is a classification explanation by protocol type.

4.1 Serial Communication and MODBUS

CI853: Supports MODBUS RTU master, COM1 master/slave, Siemens 3964R, and user-defined protocols. 2 channels, speed range 75~19200 bps. Typical fault: Communication timeout. Troubleshooting steps:

Check the RJ-45 pin definitions (3: B, 4: A, 5: common terminal).

Use a serial monitoring tool (such as an RS-485 analyzer) to confirm the physical layer waveform.

Verify whether the slave address and CRC check settings are consistent with the control program.

CI854A/CI854B: ROFIBUS DP-V1 master station, supports redundancy (CI854B), with a maximum speed of 12 Mbit/s. Common problem: Bus failure causes CPU cycle extension. Solution:

Use PROFIBUS diagnostic tools (such as PB Tester) to scan the site and locate the address of the faulty station.

Check terminal resistance: The terminal should be enabled at both ends of the station and disabled in the middle.

Ensure that the GSD file versions of the primary and backup modules are completely consistent in CI854B redundancy mode.

4.2 Industrial Ethernet Protocol

CI868/CI868A: MODBUS TCP master/slave, dual channel (CI868A is a single channel), 10/100 Mbit/s. Suitable for connecting SCADA or third-party PLCs. Troubleshooting:

Use the ping command to test IP connectivity.

Check if port 502 is blocked by the firewall.

Enable the 'Keep Alive' feature in Control Builder to prevent TCP half open connections.

CI871/CI871A: ROFINET IO device (slave), single channel, 10/100 Mbit/s. Frequently communicate with Siemens S7-1500 main station. If there is a data exchange interruption:

Confirm that the device name of CI871 matches the name configured for the main station.

Analyze network topology using PROFINET diagnostic tools such as PRONETA.

Update the CI871 firmware to the latest version (3BSE092693R1 corresponds to CI871A).

CI873/CI873A: EtherNet/IP adapter (slave) that supports communication with Rockwell Logix controllers. The fault is mainly caused by mismatched I/O connection sizes. Solution: Accurately match the length of input/output instances in RSLogix 5000.

4.3 Dedicated and Legacy Protocol

CI855: ABB S100 I/O bus master station, used to expand old S100 modules. The speed is 10 Mbit/s, with a maximum of 200 datasets per second. If I/O data is garbled, check the cleanliness of the fiber optic connector.

CI857: DriveBus master station, connected to ABB drives (such as ACS800). Single channel, 4 Mbit/s, fiber optic interface. Common malfunction: Loss of drive communication. troubleshoot

Check the fiber optic transmission/reception power (using an optical power meter, normally above -15 dBm).

Confirm that the DriveBus terminal switch position is correct (start and end ON, middle OFF).

CI862: Genius bus master station, used for GE series I/O. Speed range of 38.4~153.6 kbit/s, 4-pin Phoenix terminal. If there are a large number of retry frames, reduce the bus rate to 76.8 kbit/s and increase the scanning time.

CI869: AF100 (Advant Fieldbus 100) master station, supporting cable redundancy (dual channel). Suitable for upgrading old Advant systems. Its redundant switching does not require CPU intervention, but "Cable Redundancy" needs to be enabled in the hardware configuration.

I/O Expansion and Modular Bus Capacity Planning

5.1 Modulabus (local I/O bus)

Each CPU is connected to the local I/O cluster through the TB807 module (Modulabus terminal) on the CEX bus. Key limitations:

Non redundant CPU: 1 electrical cluster (S800 I/O through electrical port)+up to 7 fiber optic clusters.

Redundant CPU: Only fiber clusters are allowed, up to a maximum of 7.

Each I/O cluster can contain up to 24 I/O modules (12 pairs of redundant modules in redundant CPU mode). Maximum number of total I/O modules:

Non redundant: 96 modules