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LS1021A GPIO usage peculiarity

Question asked by fdm on Aug 16, 2017
Latest reply on Aug 28, 2017 by fdm



There is some information concerning GPIO pins usage in LS1021A:

Based on feedback from SW/design team If we want use all the GPIO3, we should set all the GPIO3 pin by RCW.

Include: EC1,EC2,EC3 and MDC_MDIO. You don't have option to only select subset of the GPIO3 pins. This is applicable to all GPIO ports.

416-418 EC1 = 001 GPIO3[2:14]

419-421 EC2 =001 GPIO3[15:27]

422-424 EC3 =001 GPIO3[28:31]

425-426 MDC_MDIO =01 GPIO3[0:1]

Unfortunately this information not explained in the RM.

I am not sure if I understand this right. Is it mandatory to set all 4 groups of GPIO3 related RCW bits to the "GPIO" state in order to use only two GPIO3 pins (GPIO3_13 and GPIO3_14 in that use case), thus making e.g. eTSEC3 RGMII interface unusable?


In contrast with the foregoing, one of our custom LS1021A based boards successfully uses SDHC interface and GPIO2_24 pin as GPIO output simultaneously despite of the fact that GPIO2[4:9] pins are shared with SDHC.


As far as I know, this fact is not documented so far.

Is there any additional background info on this issue?