Hi Russell,
You could take a look at the following link:
http://www.keil.com/download/docs/306.asp
Additionally, if you are developing a new USB-based application, it is recommended considering a newer LPC or Kinetis LPC microcontroller based on Cortex M4/M0+, as the LPC2xxx family is now legacy.
Hope this will be useful for you.
Best regards!
/Carlos
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