Download of PCD3 firmware fails on END command (NAK response)

FAQ #100742

If a wrong or invalid firmware is downloaded to a PCD3, the firmware download progress bar reaches 100%. After the download finished, an error message appears indicating a failure caused by a NAK response.


After the download of a firmware file the following error message from the Firmware Downloader (FWDnld) appears. The message is "Download failed on END command. Error: NAK response."

The reason for this message is a "NAK" (Not Acknowledged) response from the PCD. Before the PCD loads a new firmware, it is verified by the PCD. If this verification fails (because of e.g. a wrong checksum of the firmware of because the firmware is not intended for this CPU type), a NAK response is sent by the PCD to the Firmware Downloader.


  • Make sure the firmware you download is created for the CPU type you have attached (a firmware for e.g. the PCD2.M480 will not run on a PCD3.Mxxx0 system)

  • Make sure the file you have downloaded is not corrupted (e.g. while the download from the internet or similar). In case of doubt, re-download it.

Related Files:


PCD3 / _Firmware Classic

Last update: 29.05.2015 21:10

First release: 20.07.2007 10:15

Views: 5668

The requested software / document is no longer marketed by Saia-Burgess Controls AG and without technical support. It is an older software version which can be operated only on certain now no longer commercially available products.