Brief Product Description

Allen‑Bradley 1756-L61A is Series A version of Rockwell ControlLogix 5561 rack-based controller, belongs to ControlLogix 5560 family, equipped with 2MB user memory and 478KB I/O memory. It adopts multi-task control architecture, supports sequential control, process control, motion control and drive integration. It has built-in RS232 serial port, compatible with ControlNet, EtherNet/IP, DeviceNet and remote I/O expansion. Programmed via RSLogix5000 software. 1756-L61A is discontinued by Rockwell since June 1,2017, only surplus and refurbished tested units for legacy ControlLogix system maintenance and spare replacement.

Core Product Functions

• ControlLogix rack CPU processor, occupies one slot in 1756 chassis
• Memory: 2MB user program/data memory, 478KB I/O memory; support 1784-CF series CF card for non-volatile backup
• Max I/O points: up to 128,000 digital points; max analog I/O:4000
• Onboard RS232 serial port, support DF1, DH485, ASCII protocol
• Multi-tasking, configurable periodic tasks, support producer/consumer communication mode
• Support redundant controller configuration with 1756-RM2 redundancy module
• Integrated motion control interface for Kinetix servo drives
• Front panel mode key, run/fault/status LED indicators, battery for tag data retention
• Communicate with local/remote I/O modules over backplane and fieldbus

Application Scenarios

• Legacy Rockwell ControlLogix PLC main control cabinet
• Power plant auxiliary equipment, water treatment, chemical plant process control
• Metallurgy, packaging, printing, rubber factory motion and sequence control
• Automotive assembly line, material conveying and large machine automation
• Oil & gas pipeline, compressor station hybrid control system
• Old ControlLogix system spare replacement, maintenance and retrofit

FAQ (Frequently Asked Questions)

• Q: Controller fault or cannot go to RUN state after installing 1756-L61A?
  A: Check firmware version match with RSLogix5000, controller battery status, CF card integrity, chassis power, backplane connection, program fault and task configuration.
• Q: What is difference between 1756-L61A and 1756-L61B?
  A: A is early series revision; B series has updated hardware and firmware, better stability, mostly backward compatible; some firmware versions differ.
• Q: What software is used for programming?
  A: RSLogix5000, firmware version range for 1756-L61A starts from V12.
• Q: Is 1756-L61A available for new projects?
  A: Rockwell EOL since June 1,2017, no new original production. Recommend migration to ControlLogix 5580 or Compact 5000 controller.
• Q: Common failure points?
  A: Backup battery depletion, CF card failure, backplane connector oxidation, internal memory chip aging, firmware corruption.