SPRUJ28E November 2021 – September 2024 AM68 , AM68A , TDA4AL-Q1 , TDA4VE-Q1 , TDA4VL-Q1
In UART modes, sleep mode is enabled by setting the UART_IER_UART[4] SLEEP_MODE bit to 1 (when the UART_EFR[4] ENHANCED_EN bit is set to 1).
Sleep mode is entered when all of the following conditions exist:
Sleep mode is a good way to lower UART power consumption, but this state can be achieved only when the UART is set to modem mode. Therefore, even if the UART has no key role functionally, it must be initialized in a functional mode to take advantage of sleep mode.
In sleep mode, the module clock and baud rate clock are stopped internally. Because most registers are clocked by these clocks, this greatly reduces power consumption. The module wakes up when a change is detected on the RX line, when data is written to the TX FIFO, and when there is a change in the state of the modem input pins.
An interrupt can be generated on a wake-up event by setting the UART_SCR[4] RX_CTS_WU_EN bit to 1. To understand how to manage the interrupt, see Section 12.1.6.3.5.1.2, Wake-Up Interrupt.
There must be no writing to the divisor latches, UART_DLL and UART_DLH, to set the baud clock (BCLK) while in sleep mode. It is advisable to disable sleep mode using the UART_IER_UART[4] SLEEP_MODE bit before writing to the UART_DLL or UART_DLH register.