DSP Sleep Mode Management
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SPRUH91D–March 2013–Revised September 2016
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Power Management
9.6 DSP Sleep Mode Management
9.6.1 C674x DSP CPU Sleep Mode
The DSP CPU can be put in a low-power state by executing the IDLE instruction. For information on the
IDLE instruction, see the TMS320C674x DSP CPU and Instruction Set Reference Guide (SPRUFE8).
9.6.2 C674x Megamodule Sleep Mode
The IDLE instruction is used as part of the procedure for shutting down the entire C674x megamodule, by
the power-down controller (PDC) module. In shutting down the entire C674x megamodule, the PDC can
internally clock gate off the following components of the megamodule and internal memories of the DSP
subsystem:
• C674x CPU
• Level 1 Program Memory Controller (PMC)
• Level 1 Data Memory Controller (DMC)
• Level 2 Unified Memory Controller (UMC)
• Extended Memory Controller (EMC)
• L1P Memory
• L1D Memory
• L2 Memory
Putting the entire C674x megamodule into the low-power sleep mode is typically more useful and saves a
lot more power, as compared to just executing the IDLE instruction to put only the CPU in idle mode.
For information on putting the C674x megamodule in the low-power mode using the PDC, see the
TMS320C674x DSP Megamodule Reference Guide (SPRUFK5).
9.7 RTC-Only Mode
NOTE: To put the device in RTC-only mode, there is no software control sequence. You can put the
device in the RTC-only mode by removing the power supply from all core and I/O logic,
except for the RTC core logic supply (RTC_CVDD).
When the rest of device is powered off, there is no up mechanism from the RTC logic to
wake-up the rest of the chip or signal the external power supply on when to reapply the
power. If the device is put in the RTC-only mode, then external control/decision making logic
would be required to reapply power to the device.
In real-time clock (RTC)-only mode, the RTC is powered on and the rest of the device can be completely
powered off (core and I/O voltage removed). In this mode, the RTC is fully functional and keeps track of
date, hours, minutes, and seconds. In this mode, the overall power consumption would be significantly
lower, as voltage from the rest of the core and I/O logic can be completely removed, eliminating most of
the active and static power of the device, except for what is consumed by the RTC module, running at
32 kHz.
NOTE: The RTC is not supported on the C6745 DSP.
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