need of pul up resistor in the lines of microSD/SD cards connectors

[rvspr]

what is the need of pull up resistors in the data lines and cmd line of the sd/microsd card connectors???????????

is it mandatory???

and why it is not placed in the clk line????????

 

[alexan_e]

Usually SPI doesn't use pullup unless you have a microcontroller that has open drain outputs or very weak current sourcing capability.

Pullup resistors are used in I2C which uses open drain pins but this is a different case.