Firmware for the PLC-5 and SLC-500 controllers is a chargeable item with an associated part number and kit, which generally consists of a firmware file and official revision labels. Many PLC-5 controllers include one or more ROM chip sets for the DH+/RIO daughterboards and, for old controllers, for the controller itself.
Firmware for MicroLogix controllers is downloadable free of charge, and firmware for ControlLogix controllers is part of the Tech Connect support program.
There is a different part number for each hardware Series letter. The Series Letter designation is different from the Firmware Revision. In PLC-5 controllers, the Series reflects different hardware under the hood, and firmware for different Series controllers can't be interchanged, nor will firmware change the Series of the controller.
The part number for the firmware kit for your controller will be 1785-L80C15SERx, where x is the Series Letter of the controller.
Since you have a PLC-5/80C15 with Revision D firmware, you could have a Series D or a Series F controller. The sticker on the side will tell you for certain.
