GPMC with OSD335x C-SIP

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- May 20, 2020 at 1:31 pm #10203
  PD
  Participant
  Is it possible to use GPMC with the C-SIP? I know the lower byte pins (AD0-AD7) are unavailable because it’s shared with the eMMC, but I can’t find anything explicitly documenting whether I could (for example) leave AD0-AD7 for eMMC and pinmux AD8-AD15 as GPMC and simply use the upper byte (even if reading the lower byte returns garbage that I mask in software).
  Does having the eMMC pinmuxed on AD0-AD7 conflict with pinmuxing AD8-AD15 to GPMC? I’m looking to connect a FIFO-like expansion, so I’d just need several data bits, the GPMC clock, and maybe a couple control signals. Thanks.
- May 22, 2020 at 10:25 am #10204
  Neeraj Dantu
  Moderator
  PD,
  The best way to utilize the GPMC interface would be to use the OSD335x-SM, which does not include the eMMC and therefore can provide access to all the pins of the GPMC interface.
  Using the C-SiP for this purpose would be unnecessary, as your use case disregards the eMMC completely.
  Best,
  Neeraj
- May 22, 2020 at 11:45 am #10205
  PD
  Participant
  Thanks for the reply. To clarify my question, I’m wondering if I can retain eMMC functionality and still use a portion of the GPMC. If I leave eMMC as-is, and can pinmux only the circled pins (and maybe some control signals) in the attached image as GPMC pins, then I could still have an 8-bit wide high speed interface to an external device, even if I have to shift/mask my reads/writes, for example: byte_rx=(gpmc_in&0xFF00)>>8; or: gpmc_out=(byte_tx<<8); .
  It’s not clear to me whether pinmuxing only a portion of the GPMC is a valid configuration, without conflicting with eMMC (other peripherals seem to allow it though). Thanks.
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  gpmc.png
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GPMC with OSD335x C-SIP

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