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TMDSEVM437X: Pin Conflict For GPMC WPN

Part Number: TMDSEVM437X
Other Parts Discussed in Thread: AM4378

Hi  Sir

Below are questions about Pin Conflict for AM437x (AM437x General Purpose Evaluation Module (EVM) Schematic )

We need 4 Function to Work together on AM4378. HDMI.PRU Ethernet, MMC0-SD card, MMC1-eMMC  or NAND Flash(Alternative).

1.Function 1: HDMI. DSS -> Only One Pin can choose in PinMux Tool for DATA13.->D19,  Same chipset SIL9022 as  GP EVM board.No Pin Conflict.

2, Function 2: 100M Ethernet -> PRU MII1, Because D19 is used for HDMI, mii1_rxer has to use B3 Pin.No Pin Conflict.

3, Function 3: MMC0 For SD Card. No Pin Conflict.

4, Function 4: MMC1 For eMMC. Pinmux does not assign eMMC_Reset Pin.No Pin Conflict found.

But we check the GP EVM board, eMMC_Reset is controlled by "WPN", and it is in Conflict with MII_RXER, Pls check below (Function 5) for detail.

5.Function 5 Nand Flash:   Be note, Function 4 and Function 5 are alternatives.

Nand Flash as EVM design: AM437x General Purpose Evaluation Module (EVM) Schematic

We found "Wpn" is Pin Conflict.

In GP EVM Schematics,wpn is used for Nand Flash Write Protect。

My question is :

Because B3 is used for MII_RXER, Could we move wpn to another GPIO(For example  P25, IO Voltage is 3.3V)。

Assuming we have 2 user Cases:

Case1: The system needs to Bootup from GPMC Nand Flash(or MMC1 eMMC)。

Case2: System boot up from MMC0 SDcard only,NAND Flash(or MMC1 eMMC) are used for storage。

In which case we can move "NAND_WPN"  to another GPIO? 

For the "MMC1_RSTn" or  "NAND_WPN" signal which GPIO is suitable?


  • Qin

    You should be able to replace the WPn signal with a GPIO. The same is true for the eMMC reset. 

    The choice of GPIO will depend on your use case., 

    For WPn, you need to choose a GPIO with a reset state that matches the use case, power-up protected, or power-up unprotected. 

    For eMMC, you will need to chose a GPIO with a reset state of active 1 in order for the eMMC to be bootable. 

    Which of the GPIOs you choose will depend on what is available after configuring your primary interfaces.