1756-HIST2G | Allen-Bradley | ControlLogix FactoryTalk Historian

The Allen-Bradley 1756-HIST2G, also cataloged as the 1756-HIST2G Historian Module, operates as a dedicated hardware component for high-speed data acquisition and archival storage within ControlLogix system platforms.

Hardware Specifications

Profinet / EtherNet/IP Deterministic Networks

The 1756-HIST2G module leverages the ControlLogix backplane to intercept data tags in real-time, functioning as a data collector that maintains integrity through a precision real-time clock. Deterministic network synchronization is facilitated via the integrated 10/100T IEEE 802.3 Ethernet port, allowing for seamless integration into existing EtherNet/IP architectures. I/O density scaling and tag collection rates must be balanced against the 500 MHz AMD LX800 processor load to ensure data capture does not result in backplane latency. Firmware flash compatibility is mandatory to maintain synchronization with the host processor and to support the underlying FactoryTalk archiving services.

Frequently Asked Questions (FAQ)

Q: What is the purpose of the non-removable rechargeable lithium battery?

A: The battery is used to maintain the integrity of the 512 Kbytes of SRAM during power loss events, ensuring that time-stamped configuration data and critical runtime pointers are not corrupted upon system reboot.

Q: Does the module support hot-swapping under backplane power?

A: Yes. The module is designed for insertion and removal while the chassis is powered. However, ensure that the historian archival process is stopped or the module is in an "off-line" state within the software configuration before removal to prevent potential file system corruption on the CompactFlash media.

Field Installation Guidelines

• Chassis Placement: Install the module in any available ControlLogix chassis slot. Ensure the module is fully seated and the top and bottom latching tabs are locked to ensure stable backplane bus contact.

• Grounding: As with all 1756 series modules, the chassis must be properly bonded to the enclosure ground bus. This is critical for high-frequency noise immunity on the Ethernet communication port.

• Storage Media: When installing a Type 2 CompactFlash card, ensure the DMA pins are aligned correctly. Do not force the card into the slot, as the DMA interface is sensitive to pin misalignment.

• Thermal Management: Given the 7 W maximum power dissipation, verify that the chassis ventilation allows for sufficient airflow to keep the module temperature within operating limits, preventing thermal throttling of the AMD processor.