I am using Wiz820io (W5200) for my project and my microcontroller polls the Link status bit (Up/down) to check the ethernet cable connectivity. Generally the system is working Ok but I have noticed one problem. I am seeing is that the link status goes up and down even though the ethernet (good quality new cable) is constantly connected between router and Wiz820io. I have tested it with 3 different rounters and different ethernet cables but results are the same.
I have also noticed that the link goes up and down more often (about 40 times in 8 hours) in when there is a longer the ethernet cable (approx 25meter) is used. For short cables (1meter) it goes down 15 times in 8 hours.
Can you please tell me what could be the reason for it ?