220.127.116.11. Dedicated Clock Input Pins
You can use the dedicated clock input pins (CLK[0..23][p,n]) for high fan-out control signals, such as asynchronous clears, presets, and clock enables, for protocol signals through the GCLK or RCLK networks.
CLK pins can be either differential clocks or single-ended clocks. When you use the CLK pins as single-ended clock inputs, only the CLK<#>p pins have dedicated connections to the PLL. The CLK<#>n pins drive the PLLs over global or regional clock networks and do not have dedicated routing paths to the PLLs.
Driving a PLL over a global or regional clock can lead to higher jitter at the PLL input, and the PLL will not be able to fully compensate for the global or regional clock. Altera recommends using the CLK<#>p pins for optimal performance when you use single-ended clock inputs to drive the PLLs.
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