8.5.1.3.1 Daisy Chain Transmitter and Receiver Functionality

The daisy chain is bi-directional and half duplex, and therefore, has a transmitter (TX) and receiver (RX) on both interfaces (COMH and COML). The TX and RX functions are controlled automatically by the hardware (under certain conditions, typically during startup and reset) and by the user (under other conditions). The DAISY_CHAIN_CTRL register provides user controls for the individual interfaces. The hardware control is determined by the startup conditions: if WAKEUP is high after startup, the COML TX and COML RX are disabled and upon wakeup from a hardware shutdown (only using the WAKEUP input), the COMH and COML receivers and the COML transmitter are disabled. More information on these conditions is outlined in the Base Device Wakeup and Hardware Shutdown section. Once startup has completed, use the CONTROL2[DAISY_CHAIN_CTRL_EN] bit to select the user configurable settings in the DAISY_CHAIN_CTRL register. The DAISY_CHAIN_STAT register shows the current enable/disable status for both COMH and COML interfaces as well as the status of the control for the interfaces (Hardware vs. User). Note that after enabling COM RX, wait for at least 100usec before start communication.