Im working on reverse engineering a USB controller. The name of the controller chip is the "UD6810" which appears to be a Chinese clone of another chip (since a lot of results about it have been removed from google via dcma requests). I've found a program which can successfully flash the firmware however I obviously need to determine the instruction set before I can modify it. Datasheets i've found on the web seem to be missing this key information and docs are generally quite hard to find. I have the binary code since I can both see it in the flashing program's files and capture it in the USB traffic as it flashes the chip. How can I determine the instruction set?

I'm working on reverse engineering a USB controller. The name of the controller chip is the "UD6810" which appears to be a Chinese clone of another chip (since a lot of results about it have been removed from Google via DMCA requests). I've found a program which can successfully flash the firmware.

However, I obviously need to determine the instruction set before I can modify it. The datasheets I've found on the web seem to be missing this key information and docs are generally quite hard to find. I have the binary code since I can both see it in the flashing program's files and capture it in the USB traffic as it flashes the chip. 

How can I determine the instruction set?