Hi,
in case of MPC5xxx devices, it's proprietary SW from Pemicro. All the resources can be found on their web page:
https://www.pemicro.com/opensda/
Here is the link to firmware package:
http://www.pemicro.com/downloads/download_file.cfm?download_id=378
In case of any issues:
https://www.pemicro.com/support/index.cfm
Regards,
Lukas