MCP23008 data sheet shows 3 modes (100 kHz, 400 khz, 1.7 MHz). I find no further explanation of it in the document. Do I need to to be concerned with it or just proceed with the I2C protocol like any other chip?

  • 1
    \$\begingroup\$ What is it you have in mind more specific? \$\endgroup\$
    – MiNiMe
    Oct 21, 2023 at 21:08

1 Answer 1


100 kHz, 400 kHz, and 1.7 MHz correspond to Sm, Fm, and Hs modes. The Wikipedia article explains the modes. The tables in the spec explain the differences that you need to be aware of.

The chip doesn't seem to be fully compliant with Hs mode, so if you want to run faster than 400 kHz, you need to read the spec very carefully.

Use 100 kHz or 400 kHz and things should go smoothly.

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Table from: https://en.wikipedia.org/wiki/I%C2%B2C

Chip spec: https://ww1.microchip.com/downloads/en/DeviceDoc/MCP23008-MCP23S08-Data-Sheet-20001919F.pdf


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