Manufacturer Access (MAC) commands are defined by Texas Instruments. MAC commands require a write to the AltManufacturerAccess() registers at 0x3E and 0x3F, and then an additional write to the AltManufacturerAccess() sub-command being used. The complete list of all MAC commands in the BQ27Z746 and an example of a Command Write operation with MAC commands can be found in the 0x00, 0x01 ManufacturerAccess() and 0x3E, 0x3F AltManufacturerAccess() chapter of the BQ27Z746 Technical Reference Manual.

Example: Read Chemical ID() to AltManufacturerAccess().

1. Send Chemical ID() to AltManufacturerAccess().
   1. I2C Address (Hex) = AA
   2. Start Register (Hex) = 3E
   3. Bytes to Write (Decimal) = 06 00 (this write data must be written in little endian)
2. Read the result from AltManufacturerAccess() and MACData().
   1. I2C Address (Hex) = AA
   2. Start Register (Hex) = 3E
   3. Number of Bytes to Read (Decimal) = 36
3. View the results in Transaction Log.
   1. The first two bytes "06 00" is the MAC command (for verification)
   2. The second two bytes "09 59" are the ChemID in little-endian (the ChemID can be seen if the CHEM_ID button is checked in the Command window)
   3. The final two bytes is the checksum and length. The length here is 6. The checksum is 0xFF - (sum of the first length - 2 bytes). The length and checksum are used to validate the block response.

Figure 9-2 shows this in bqStudio. To perform this process, fill out all of the fields as shown, then click Write and Read.