When using ADIN1200 in MII mode, the clock drops from 25MHz to 2.5MHz when link down is detected.

Hi,
This behavior is expected. The MII clocks are speed dependent, 25 MHz for 100BASE‑TX and 2.5 MHz for 10BASE‑T, so when the link drops the ADIN1200 keeps TX_CLK running but idles at 2.5 MHz which is 10 Mb/s timing; this occurs even when autonegotiation is disabled and 100 Mb/s full‑duplex is forced, because the standard ties the MII clock rate to the active/resolved link speed, not to a forced speed setting in link down.

Do you require a continuous 25 MHz clock even during linkdown? If so, what uses it, and what fails when it drops to 2.5 MHz?

regards,

Mark

Hi,
This behavior is expected. The MII clocks are speed dependent, 25 MHz for 100BASE‑TX and 2.5 MHz for 10BASE‑T, so when the link drops the ADIN1200 keeps TX_CLK running but idles at 2.5 MHz which is 10 Mb/s timing; this occurs even when autonegotiation is disabled and 100 Mb/s full‑duplex is forced, because the standard ties the MII clock rate to the active/resolved link speed, not to a forced speed setting in link down.

Do you require a continuous 25 MHz clock even during linkdown? If so, what uses it, and what fails when it drops to 2.5 MHz?

regards,

Mark

Thank you for your reply.
25MHz will be continuously required.
This is an EOL replacement project, and in the current system, MII also supplies 25MHz when the link goes down, so we would like to keep it the same.

Hi,

Unfortunately, the default behavior of the ADIN1200 TX_CLK follows the linkup speed and will default to 10Mbps when the link is down. There is no register available in ADIN1200 to alter this behavior. 

regards,

Mark