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MSP432E401Y: EPI Interface

Perry Ferren
Prodigy 140 points
Part Number: MSP432E401Y

We are using the MSP432E401YTPDTR EPI interface in host-bus mode, dual chip select mode. The peripheral interface is configured at address A000,0000. It is a 16M bit (2MB) MRAM device. We are trying to limit the chip select to this device to the entire size of the memory, but it seems the EPSZ settings in the EPIADDRMAP register limits the device size settings to

0x0 = 256 bytes; lower address range: 0x00 to 0xFF

0x1 = 64 KB; lower address range: 0x0000 to 0xFFFF

0x2 = 16 MB; lower address range: 0x000000 to 0xFFFFFF

0x3 = 256 MB; lower address range: 0x0000000 to 0xFFFFFFF

If we use 0x2, we have no issue accessing the entire device, however, still get chip selects triggered when accessing beyond the 2MB device addresses which results in data being written to the MRAM which is unwanted. The condition as highlighted below. Is there a way to limit the chip select to only the size of the device (2MB). 

External Peripheral Size This field selects the size of the external peripheral.

If the size of the external peripheral is larger, a bus fault occurs.

If the size of the external peripheral is smaller, it wraps (upper

address bits unused).

Thanks In Advance

Perry Ferren

  • 0
    TI__Guru*** 135355 points

    Hello Perry,

    No, there is not a way to limit the chip select to only 2MB at a peripheral level. You'd have to ensure that the software doesn't try and read from higher addresses through the EPI interface.

    Alternatively you could investigate if it would be viable to not use the chip select of the EPI but instead control a GPIO manually. I'm not familiar with MRAM so I don't know if there are any timing concerns with the chip select toggles that would prevent that, but wanted to offer that as another idea for consideration.

    Best Regards,

    Ralph Jacobi