
ML674001 Series/ML675001 Series User’s Manual
Chapter 7
Power Management
7-1
Chapter 7
Power Management
7.
7.1
Overview
This LSI was designed with advanced power saving features to enable flexibility in optimizing power
consumption. As such, a great level of configurability has been built into the power management block. This is
achieved by varying the frequency of clock signal to different blocks or by stopping the clock signal entirely to
certain designated blocks.
To save power, a user application system that does not need the DRAM controller, can save energy by disabling
this unit through configuring the Mode Selection (DRAME_N) pins as explained in chapter 4 of this manual.
This has the effect of disable the clock signal input to this block and thus shutting them down. Note, however,
that this modification cannot be undone in software. Furthermore, manipulating the input signals in hardware,
after the MCU has been powered up, not only does not work, but also risks unreliable operation.
Note:
For further details on the DRAME_N signals, see Chapter 4 “Chip Configuration.”
Two CPU modes allow software to selectively reduce power consumption: STANDBY stops the system clock
oscillation entirely; HALT mode stops the clock signals to the following functional blocks: CPU, system bus,
bus control circuitry, and memory controller interfaces to built-in RAM and external memory.
The software can save energy by stopping clock signals to individual function blocks.
The software can also save energy by dynamically changing the HCLK or CCLK frequency to 1/1, 1/2, 1/4, 1/8,
1/16, or 1/32* times the base frequency.
(* 1/32: ML675001 Series only)
Note:
For further details, see “Clock Gear” below.
7.2
Power Management Functions
The following Table summarizes the power management functions available to software;
Figure 7.1 gives a state
transition diagram.
Operating
Mode
Stopping or
Changing Clock
Restarting clock
signals
RUN
All functional blocks operative
RUN
Stop clock signals to individual functional
blocks
Software control
Software
RUN
Clock gear
Software control
Software
HALT
Stop clock signals to CPU, system bus, etc.
Software control
Interrupt or reset
STANDBY
Stop clock oscillation
Software control
External interrupt, port
input, or reset
Note:
HALT mode stops the clock signals to the following functional blocks: CPU, system bus, bus control circuitry,
and memory controller interfaces to built-in RAM and external memory.