I am looking at the schematic of IMX6SOLOX_SABRESDB-DESIGNFILES then noticed there are 10 Ω dumping resistors on each SD clock lines(R53, R94 and R83).
When R83 on SD4_CLK were replaced with 0 Ω resistor, I obserbed the SD card could not work with SD4 ports.
The below is the picture of SD4_CLK with 0 Ω resistor on i.MX6 side, there is a spike on the rising edge.
But the there is no spike on the SD4_CLK on SD card side. (see below)
In case of R83 with 33 Ω resistor, SD card works.
Then I have some questions.
What are the purpose of those resistors and why are those needed?
Dose the spike on SD4_clock affect the data sampling for receiving data from the SD card?