Restricted Fmax due to minimum period

Apologize for the confusion earlier!

Regarding the clock tree and restricted Fmax:

Frank absolutely right that restricted Fmax is tied to the clock pulse width limitations, and this is primarily influenced by the LE register switching behavior (how fast the FPGA can reliably process and latch clock signals, not the IO performance).

So, the timing constraint you see (due to restricted Fmax) is actually an issue of how fast the registers can be reliably triggered by the clock signal, not the speed of the IO signal itself.

Frank is also right on: restricted Fmax (tmin) refers to the core logic's clock pulse width limitation and not the I/O path. It’s about the minimum period required for registers, not the I/O toggle rate. Running a timing analysis with the C6 speed grade will reveal I/O-related Fmax separately.

Table 19 provides maximum data rates for I/O standards like LVDS but doesn’t consider voltage swing. The voltage swing does not directly affect the max data rate; it’s more about signal integrity and ensuring compliance with the I/O standard.

For LVDS data rates up to 700 Mbps, you need DDR input registers to process both rising and falling clock edges, which is crucial for double-data-rate signaling.