SLUSE91B September 2020 – January 2022 BQ769142
PRODUCTION DATA
The HDQ interface is an asynchronous return-to-one protocol where a processor communicates with the BQ769142 device using a single-wire connection to the ALERT pin or the HDQ pin, depending on configuration. Both the master (host device) and slave (BQ769142) drive the HDQ interface using an open-drain driver, with a pullup resistor from the HDQ interface to a supply voltage required on the circuit board. The BQ769142 device can be changed from the default communication mode to HDQ communication mode by setting the Settings:Configuration:Comm Type configuration register, or sending a subcommand (at which point the device switches to HDQ mode immediately). Note that the SWAP_COMM_MODE() subcommand immediately changes the communications interface to that selected by the Comm Type configuration, while the SWAP_TO_HDQ() subcommand immediately changes the interface to HDQ using the ALERT pin.
With HDQ, the least significant bit (LSB) of a data byte (command) or word (data) is transmitted first.
The 8-bit command code consists of two fields: the 7-bit HDQ command code (bits 0–6) and the 1-bit R/W field (MSB Bit 7). The R/W field directs the device to do one of the following:
The HDQ peripheral on the BQ769142 device can transmit and receive data as an HDQ slave only.
The return-to-one data bit frame of HDQ consists of the following sections: