Low-Power Mode
1270
SPNU503C – March 2018
Copyright © 2018, Texas Instruments Incorporated
Serial Communication Interface (SCI)/ Local Interconnect Network (LIN)
Module
25.10.2.2 Transmitting Data in Multi-Buffer Mode
Multi-buffer mode is selected when the MBUF MODE bit is set to 1. Like single-buffer mode, you can use
the polling, interrupt, or DMA method to write the data to be transmitted. The transmitted data has to be
written to the LINTD0 and LINTD1 registers, based on the number of bytes. LIN waits for data to be
written to Byte 0 (TD0) of the LINTD0 register and transfers the programmed number of bytes to
SCITXSHF to transmit one by one automatically. If the checksum scheme is enabled by setting the Send
Checksum (SC) bit to 1, the checksum will be sent after transmission of the last byte of the programmed
number of data bytes, indicated by the LENGTH field. The SC bit will be cleared after the checksum byte
has been transmitted.
25.11 Low-Power Mode
The SCI/LIN module can be put in either local or global low-power mode. Global low-power mode is
asserted by the system and is not controlled by the SCI/LIN module. During global low-power mode, all
clocks to the SCI/LIN are turned off so the module is completely inactive. If global low-power mode is
requested while the receiver is receiving data, then the SCI/BLIN completes the current reception and
then enters the low-power mode, that is, module enters low-power mode only when Busy bit (SCIFLR.3) is
cleared.
The BLIN module may enter low-power mode either when there was no activity on the LINRX pin for more
than 4s (this can be either a constant recessive or dominant level) or when a Sleep Command frame was
received. Once the Timeout flag (SCIFLR.4) was set or once a Sleep Command was received, the
POWERDOWN bit (SCIGCR2.0) must be set by the application software to make the module enter local
low-power mode. A wakeup signal will terminate the sleep mode of the LIN bus.
NOTE:
Enabling Local Low-Power Mode During Receive and Transmit
If the wakeup interrupt is enabled and low-power mode is requested while the receiver is
receiving data, then the SCI/LIN immediately generates a wake-up interrupt to clear the
powerdown bit. Thus, the SCI/LIN is prevented from entering low-power mode and
completes the current reception. Otherwise, if the wakeup interrupt is disabled, the SCI/LIN
completes the current reception and then enters the low-power mode.
25.11.1 Entering Sleep Mode
In LIN protocol, a sleep command is used to broadcast the sleep mode to all nodes. The sleep command
consists of a diagnostic master request frame with identifier 0x3C (60), with the first data field as 0x00.
There should be no activity in the bus once all nodes receive the sleep command: the bus is in sleep
mode.
Local low-power mode is asserted by setting the POWERDOWN bit; setting this bit stops the clocks to the
SCI/LIN internal logic and registers. Clearing the POWERDOWN bit causes SCI/LIN to exit from local low-
power mode. All the registers are accessible during local power-down mode. If a register is accessed in
low-power mode, this access results in enabling the clock to the module for that particular access alone.