i2c bank switching

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Bank Switching Operation

I2C can access 256 addresses directly (i.e. 0x00 through 0xFF).

SMBus can access 128 addresses directly (i.e. 0x00 through 0x7F).

NB3H5150 has an address space which goes up to 0x14F. Therefore, a “bank switching” mechanism is included to allow access to all addresses no matter which bus protocol is used. Effectively, the two bank select bits are appended to the most-significant end of the seven-bit byte offset, creating a nine-bit address. The bank switch control bits(6:7) are located in Register 0x21.

The most significant two bits of that register are used for bank selection; the least significant six bits are used for the READBYTECOUNT Function.

[링크 : http://www.onsemi.com/pub_link/Collateral/NB3H5150_I2C_MANUAL.PDF]