24.5.4.3.2 Client Address Masking

The I2CxMSK register masks the address bit positions, designating them as don’t care bits for both 10-bit and 7-bit Addressing modes. When a bit in the I2CxMSK register is set (= 1), the client responds when the bit in the corresponding location of the address is a ‘0’ or ‘1’. For example, in 7-bit Client mode with I2CxMSK = 0100000, the client module Acknowledges addresses ‘0000000’ and ’0100000’ as valid.