The PLC 1756-L72 is a ControlLogix Series Programmable Automation Controller (PAC). It has an available 4 MB user memory for data and logic and 0.98 MB I/O memory. The controller ships with a 1 GB SD card, the 1784-SD1, that you can use as optional nonvolatile memory storage. You can also upgrade it to 2 GB via the 1784-SD2 card if the storage is not enough for your use. It is recommended that the SD card is installed to the controller and to only use those that are sold by PLC Automation, as these cards have been fully tested to work with the controllers. Using other SD cards poses a risk of experiencing data loss or corruption. The SD cards are primarily used to store diagnostic data that is written automatically when a fault occurs. These data are used by PLC Automation for troubleshooting purposes. The 1756-L72 controller also comes with three capacitor energy storage modules. The 1756-ESMCAP/1756-ESMCAPK is a removable module available in every controller. Another removable module is the 1756-ESMNSE/1756-ESMNSEK that has no residual WallClockTime power backup. The only nonremovable module is the 1756-ESMNRM/1756-ESMNRMK that helps prevent USB connection and SD card use to help secure the controller.
