Is Pull-up of DQ /RWDS required?

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KeTa_1341526
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Hello,

[Question]

Is Pull-up of DQ / RWDS required?

[Background]

In P.25 [7. Interface States] of the following materials, it is stated that DQ / RWDS is in High-Z state during Cold / Warm Reset or Standby.

https://www.cypress.com/file/213356/download

I think this requires the Master MCU to place the bidirectional pins in the High-Z state.

In other words, since Hyper Flash and MCU are in High-Z state with each other, I think it is necessary to prevent latch-up due to shoot-through current.

In order to prevent this, it is the recognition that pull-up must be attached to the signal line.

However, when I looked at the schematic of the reference board (IMXRT1050-EVK) below, there was no external pullup.

https://www.nxp.com/docs/en/nxp/application-notes/AN12239.pdf

Is Pull-up unnecessary?

Best regards,

Takahashi

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1 Solution
SudheeshK
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Hello,

Pull up resistors on RWDS and DQ lines are not required.

Thanks and Regards,

Sudheesh

View solution in original post

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7 Replies
SudheeshK
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Hello,

Pull up resistors on RWDS and DQ lines are not required.

Thanks and Regards,

Sudheesh

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KeTa_1341526
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Distributor - TED (Japan)
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Hello,

Thanks.

But,

Why isn't the pull-up resistor needed?

Is there no problem if both Hyper Flash and MCU are in High-Z state?

Best regards,

Takahashi

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Hello,

In high-z state, both MCU and HyperFlash won't be driving any data on DQ and RWDS signals. So, there won't be any issues, if you do not use a pull up resistor on these lines.

Thanks and Regards,

Sudheesh

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KeTa_1341526
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Sudheesh-san,

DQ/RWDS is bidirectional pin.

Is the input buffer of hyper flash not enabled in the High-Z state(IDLE state)?

If the input buffer is valid, is there no problem if the signal level is high-z?

Best regards,

Takahashi

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Hello,

No, input buffer will not be enabled in High-Z state.

Thanks and Regards,

Sudheesh

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KeTa_1341526
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Hello,

For example, in the case of Read transaction, is it OK to think that the DQ port of Hyper Flash is transiting as follows?

pastedImage_0.png

Best regards,

Takahashi

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Hello,

Sorry for the delay.

I discussed your query with our experts. Your understanding about the state of DQ signals during a read operation is correct.

Thanks and Regards,

Sudheesh

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