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AM2432: MMCSD Signals

Mari Tsunoda
Expert 5726 points

Part Number: AM2432

Hi Team,

My customer has a question as follows:

About SDCD SDWP signals polarity.
In TRM Table 12-4338. MMCSD1_PRESENTSTATE Register Field Descriptions, I can see the description as follows.
Bit18 CARD_DETECT
Card Detect Pin Level
This bit reflects the inverse value of the SDCD# pin.
0h: No Card present (SDCD# = 1)
1h: Card present (SDCD# = 0)
The signal SDCD# seems to be a NEGATIVE LOGIC signal.
but in datasheet Table 6-61. MMC1 Signal Descriptions, it's "MMC1_SDCD" which seems to be a POSITVE LOGIC signal.
Specifically, When Hi level is input to MMC1_SDCD, Is it recognized as "No Card present" or "Card present"?

Same as SDWP signal.
Bit19 WRITE_PROTECT
Write Protect Switch Pin Level
The Write Protect Switch is supported for memory and combo
cards.This bit reflects the SDWP# pin.
0h: Write protected (SDWP# = 1)
1h: Write enabled (SDWP# = 0)
When Hi level is input to MMC1_SDWP, Is it recognized as "Write protected" or "Write enabled"?

Best regards,

Mari Tsunoda

  • +1
    TI__Mastermind 33633 points

    Hey Mari,

    The SDCD and SDWP signal functions are defined by industry specifications. It is important not to confuse the physical layer signal requirements with the IP register definitions. 

    Signal/Physical Layer Definitions:

    Card Detect (MMC1_SDCD)

    0 (Logic Low - VSS) = Card Detected

    1 (Logic High - VDD) = No Card Detected

    Write Protect (MMC1_SDWP)

    0 (Logic Low - VSS) = Write Protection Disabled (Write Enabled)

    1 (Logic High - VDD) = Write Protection Enabled (Write Disabled)

    The IP registers and associated bitfield definitions are not necessarily required to exactly reflect the logical truth table defined by the physical layer specification.

    Best Regards,

    Zackary Fleenor

  • 0 in reply to Fleenor
    TI__Expert 5726 points

    Hi Zack,

    Thanks for your quick response! Will forward to customer.

    Best regards,
    Mari