Module Operation
441
SPNU503C – March 2018
Copyright © 2018, Texas Instruments Incorporated
Real-Time Interrupt (RTI) Module
13.2.6 Low Power Modes
Low power modes allow the trade off of the current used during low power versus functionality and fast
wakeup response. All low power modes have the following characteristics:
•
CPU and system clocks are disabled.
•
Flash banks and pump are in sleep mode.
•
All peripheral modules are in low power modes and the clocks are disabled (exceptions to this may
occur and would be documented in the specific device data sheet).
Flexibility in enabling and disabling clocks allows for many different low-power modes (see
The operation of the RTI Module is guaranteed in Run, Doze and Snooze modes. In Sleep mode, all
clocks will be switched off and the RTI will not work.
In Doze and Snooze modes, the RTI is active and is able to wake up the device with compare, timebase
and overflow interrupts. The compare interrupts can be used to periodically wake up the device. The
overflow interrupt can be used to notify the operating system that a counter overflow has occurred.
Capturing events generated by the Vectored Interrupt Module (VIM) is also possible since, in both of these
low power modes, the peripheral modules are able to generate interrupts that can trigger capture events.
Capturing events while in Sleep mode is not supported as the clock to the RTI is not active.
When the device is put into low power mode, the peripheral which is generating the external clock NTU is
no longer active, and the timebase control circuitry has to switch to an internal clocking scheme when it
detects a missing clock on NTU. The timebase interrupt will wake up the device and the application
software has to adapt the periodic interrupt generation to the internal clock source.
DMA transfers will be disabled, and DMA requests will not be generated after device wakeup since the
DMA controller will be powered down.
NOTE:
RTICLK in Doze Mode
In the special case of Doze Mode with PLL off, RTICLK might have a different period than
with PLL enabled since RTICLK will be derived from the oscillator output. It has to be
ensured that the VCLK to RTICLK ratio is at least 3:1.
13.2.7 Halting Debug Mode Behaviour
Once the system enters halting debug mode, the behavior of the RTI depends on the COS (continue on
suspend) bit. If the bit is cleared and halting debug mode is active, all counters will stop operation. If the
bit is set to one, all counters will be clocked normally and the RTI will work like in normal mode. However,
if the external timebase (NTU) is used and the system is in halting debug mode, the timebase control
circuit will switch to internal timebase once it detects the missing NTU signal of the suspended
communication controller. This will be signaled with an TBINT interrupt so that software can resynchronize
after the device exits halting debug mode.