Looks like I found the answer to my own question on page 17 of the datasheet:
The bq77PL900 has two operational modes, stand-alone mode and host-control mode. The mode is switched by STATE_CONTROL [HOST]. In stand-alone mode, the battery protection is managed by the bq77PL900 without the need for any external control. In this mode, the CHG and DSG FETs are driven ON and OFF automatically and cell balancing is processed by a fixed algorithm if enabled by OCDELAY[CBEN]). In this mode, I2C communication is enabled, and a host can read the registers and set STATE_CONTROL [HOST] but cannot control any output or function such as Vcell AMP enable.
