I have two devices that I'd like to use together, connected via their SDIO pins. The MCU can transfer data up to 200 MB/s with a 200 MHz clock speed (HS-200). The wireless module that I want to use with the MCU can only work up to 104 MB/s with a 208 MHz clock speed (SDR104). In order to use these two devices, do I need to use a bus speed that both devices can handle, i.e. SDR104? Or could I run the MCU at 200 MHz for HS-200 even though the other module can only transfer at SDR104 rates?

For reference, this would be using the NXP RT600 MCU and 88W8987 wireless module.

  • \$\begingroup\$ Need more info, like what comm protocol your using. \$\endgroup\$
    – Voltage Spike
    Jan 22, 2021 at 18:48
  • \$\begingroup\$ @VoltageSpike What do you mean by comm protocol? For the wireless end, it will be running 802.11ac. Communication between devices will be carried out via SDIO 3.0. \$\endgroup\$ Jan 22, 2021 at 19:07
  • \$\begingroup\$ @VoltageSpike I believe the comm protocol is SDIO \$\endgroup\$
    – user253751
    Jan 22, 2021 at 19:24
  • 1
    \$\begingroup\$ It sounds like your limit will be 100 MB/s (well, Msomething -- your question doesn't convince me that you are being careful about bits vs bytes, this distinction will matter a lot more than 100 vs 104) because the MCU limits the clock rate to 200 MHz and the wireless module transmits data at 4 bits every clock cycle, so a byte every two cycles. \$\endgroup\$
    – Ben Voigt
    Jan 22, 2021 at 19:29

1 Answer 1


as you said, the CPU handles 200MB/s at a clock speed of 200MHz, that is assume a 8-bits bus clocked by 200MHz. the SDIO is 4 bits data bus, therefore at 208MHz SDR, it gives 104MB/s. in order for it to work, you will need to interface 4bits data bus from CPU to SDIO at a clock speed it can accept. It is OK your CPU runs interface clock speed at 200MHz if that is the MAX it can provide. but since SDIO is only 4 bits bus, so your CPU side will have to follow that throughput. usually uC have SDIO dedicated interface, that should interface with standard SDIO device.


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