What's the fastest I can clock data out of a serialised 1-bit port using an external clock? From the docs it looks like 60MHz. Is this true?
:shock:
Clocking Data Out Using an External Clock
That's right. The maximum input frequency on a 1 bit port pin that can be used as a the source for a clock block is 60MHz. That's true on both the XS1-G and XS1-L series devices.