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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
Solved! Go to Solution.
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Hello,
Pull up resistors on RWDS and DQ lines are not required.
Thanks and Regards,
Sudheesh
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Hello,
Pull up resistors on RWDS and DQ lines are not required.
Thanks and Regards,
Sudheesh
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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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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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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?
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