Configuration Clock Source

Specifies the clock source for device initialization (the duration between CONF_DONE signal went high and before INIT_DONE signal goes high). In 20nm or prior device families, three options are available when AS x1 or AS x4 configuration mode is not selected, which are Internal Oscillator (default value), DCLK pin, and CLKUSR pin.

For AS x1 or AS x4 configuration mode, you can select either tInternal Oscillator or CLKUSR pin only. The DCLK pin is an illegal option for AS mode. In 14nm device families, only Internal Oscillator or OSC_CLK_1 pins are available.