The PLC 1756-L55M23 is a ControlLogix Controller in the Logix5000 family of controllers. It has 1.5 KB of data and logic memory, 208 KB of I/O memory, and an integrated nonvolatile backup memory. The 1756-L55M23 has a Logix CPU as well as a backplane CPU to divide its resources. Application codes and messages are executed by the Logix CPU and the backplane CPU sends and receives data from the backplane and it communicates with I/O.
The 1756-L55M23 controller is connected to the workstation or another controller via the serial port. A 1756-CP3 serial cable is used to connect the controller to the workstation. For communication with other devices, it uses various networks like Ethernet/IP, ControlNet, DeviceNet, etc. The 1756-L55M23 can produce and consume system-shared tags over the EtherNet/IP or the ControlNet networks. One connection each is required for both the producer and the consumer.
The 1756-L55M23 controller has a multitasking feature which lets processing time be allocated to different operations in the application. It also contains programs for the group data and logic. It provides routines for encapsulating executable code in a single programming language. It supports Logix5000 programming languages both online and offline. In case of any I/O communication failure, it has an I/O LED that flashes green. It also contains a fault handler for diagnostics. The 1756-L55M23 supports the 1756-BA1 or the 1756-BATM battery, either of which need to be regularly maintained.
