SEMC_DQS and FLEXSPI_DQS signal in iMXRT117x

[Javiurb]

Hi,

I'm in a new design with iMXRT117x. I know if I don't leave DQS pins floating, I won't be able to drive the SEMC and FLEXSPI to its maximum speed. But what is the maximum speed I could achieve? 60MHz?

Thank you.

[Pavel_Hernandez]

Hello, my name is Pavel, and I will be supporting your case, I recommend reviewing the datasheet in chapter 4.5 External memory interface.

Best regards,
Pavel

[Javiurb]

Thank you Pavel for the answer,

In FLEXSPI the maximum frecuency would be 60MHz with the configuration FlexSPIn_MCR0[RXCLKSRC] = 0X0 and I could use DQS pin with another function, is it correct?

But in SEMC, I don't see the maximum frecuency if I use DQS pin with another function, is it ASYNC mode or is ASYNC with DQS pin floating?. If it is ASYNC mode, maximum frecuency in write operation would be 200MHz and in read operation (minimum time 7,1ns (setup) + 0ns (hold) ->) 140MHz, is this correct?

[Pavel_Hernandez · Accepted solution]

Hello,

In FLEXSPI the maximum frequency would be 60MHz with the configuration FlexSPIn_MCR0[RXCLKSRC] = 0X0. 
yes

I could use DQS pin with another function, is it correct?
If you use the MCR0[RXCLKKSRC] =0, you can use the pin.

But in SEMC, I don't see the maximum frecuency if I use DQS pin with another function, is it ASYNC mode or is ASYNC with DQS pin floating?If it is ASYNC mode, maximum frecuency in write operation would be 200MHz and in read operation (minimum time 7,1ns (setup) + 0ns (hold) ->) 140MHz, is this correct?
Maximum frequency of the module  200MHz.

Best regards,
Pavel

[Javiurb]

But in SEMC, I don't see the maximum frecuency if I use DQS pin with another function, is it ASYNC mode or is ASYNC with DQS pin floating?If it is ASYNC mode, maximum frecuency in write operation would be 200MHz and in read operation (minimum time 7,1ns (setup) + 0ns (hold) ->) 140MHz, is this correct?
Maximum frequency of the module  200MHz.

Regardless of the mode (ASYNC or SYNC) the maximum frecuency is 200MHz for read and write operation?

If I configure MCR[DQSMD] = 0, I could use the pin for another function?

[Pavel_Hernandez]

Hello, sorry for the late response, review the information from the datasheet.

Dummy read strobe generated by FlexSPI controller and looped back internally (FlexSPIn_MCR0[RXCLKSRC] = 0x0)

If you use the MCR0 with the internal loop you could use the pin, and the other the maximum of the module is 200 MHz for both operations, but this depends on the capacitance and the length of the pads.

Best regards,
Pavel

[Javiurb]

Thank you Pavel, my doubts are solved.

Have a nice day.