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7-bit & 10-bit I2C

hi,

Can 7-bit addressed device & 10-bit addressed device be on same I2C bus simultaneously at a time?

  • Moving to the correct forum.

  • According to the I2C spec, UM10204, section 3.1.11, page 15, titled "10-bit addressing":

    "10-bit addressing expands the number of possible addresses. Devices with 7-bit and
    10-bit addresses can be connected to the same I2C-bus, and both 7-bit and 10-bit
    addressing can be used in all bus speed modes. Currently, 10-bit addressing is not being
    widely used."

  • hi,

    my question is can the devices with 7-bit & 10-bit address be connected to same bus simultaneously?

  • Yes, they can be connected to the same bus simultaneously. If they could not be attached simultaneously, the I2C spec would not say that they can be on the same bus at all. The word "simultaneous" is implied.

    Address conflicts could still be a problem, but address conflicts (where multiple slave devices have the same address) are also a problem when only 7-bit slave address devices are used.

    Are you talking about a specific device that has a 10-bit address? As the I2C spec say, "Currently, 10-bit addressing is not being widely used" and I am not familiar with any parts that use a 10-bit address.

  • 10-bit capable devices use two bytes for addressing, of which the first byte (which coincide with the 7-bit capable device address) carry "address" out of the 7-bit range.

    Therefore no conflicts possible, and 10-bit devices can transparently share the same i2c bus with 7-bit devices. They just will not notice presence of each other.

  • hi,

    but, 1111 0XXX can be slave address of some other 7-bit device. so next byte may be considered as data by 7-bit address device, which actually was second byte of address for 16-bit addressed device.