Hi all,
I want to connect an STM32H573 device to a LAN8742A to create an Ethernet interface.
Is there any board hardware guidelines available for this ?
The LAN8742A is used in REF_CLK OUT mode (50 MHz clock output from the PHY routed to the RMII_REF_CLK input of the STM32).
When looking at the datasheet of LAN8742A, page 110 of the datasheet TX, TXEN setup time to rising edge of REFCLKO is 7.5ns minimum. (Tsu)
When looking at the datasheet of SMT32H753VI for rev V electrical characteristics Td(TXD) is 11ns maximum (transmit data valid delay time).
Then for a 50MHz clock (20ns clock period), the maximum propagation delay of REF_CLK_OUT from LAN8742A to STM32 + maximum propagation delay of TX data from STM32 to LAN8742A should be lower than : 20ns - 11ns -7.5ns = 1.5ns.
There is no information into STM32H753VI datasheet from RMII_REF_CLK rising edge and invalid TX data.
This information is needed to compute minimum propagation delay of REF_CLK_OUT from LAN8742A to STM32 + minimum propagation delay of TX data from STM32 to LAN8742A + minimum clock to invalid output (into STM32) . This value should be higher than 2ns (minimum hold time Thold of LAN8742A as per the datasheet).
Regards,
Philippe
