I am using 2 transceiver channels of Cylcone 10. I have connected the CLKUSR pin to GND in my design. Is it a must to connect external clock to CLKUSR pin for the functionality of Transceiver section. I am operating at very low speed, around 1Gbps.
No, We've to use CLKUSR pin with an oscillator for transceivers.
Refer Transceiver PHY User Guide & pin connection guideline for more information.