
POWER MANAGEMENT
S3C3410X RISC MICROPROCESSOR
15-2
POWER MANAGEMENT OPERATION
NORMAL MODE
In Normal mode, all peripherals and the basic blocks: such as CPU core, bus controller, memory controller,
interrupt controller, and clock controller, should work normally. In Normal mode, the power consumption will be
maximized.
SLOW MODE
The Slow mode can reduce power consumption by slowing down operation frequency. The operating frequency is
divide by n of MCLK. The divide ratio is determined by CS bits in the SYSCON register.
IDLE MODE
IDLE mode is invoked by the setting SYSCON[1] to "1". In IDLE mode, the operation of CPU is halted by
disconnecting the clock to CPU while some peripherals remain active.
These are two ways to escape from IDLE mode:
1.
Execute a reset. All system and peripheral control registers are reset to their default value and the contents
of all data registers are retained. The reset automatically selects a slow clock (1/16) because SYSCON[5:3]
are cleared to "000b". if interrupt masked, a reset is the only way to escape from IDLE mode.
2.
Any active interrupt happens, causing IDLE mode to be released. The interrupt routine will be serviced by
active CPU. After the interrupt is serviced, the CPU will return to the next instruction after instruction used for
IDLE mode entrance.
DMA IDLE MODE
The DMA Idle mode can be invoked by the setting SYSCON[2] to "1". In DMA Idle mode, CPU operation will be
stopped while some peripherals remain active. This is same as IDLE mode. The difference between IDLE and
DMA IDLE mode is that any external DMA request can wake up CPU and make CPU sleep by the corresponding
DMA Acknowledge. Consequently, user can make CPU alive only during the DMA operation. This mode is
effective when there are infrequent external DMA request based on Single DMA Request/Acknowledge. This
mode is not effective for internal DMA request, Demand, or Block transfer mode. The main reason for this mode
is that we can save the power consumption during DMA operation by sleeping CPU when user want DMA
operation without CPU operation and when there are infrequent external DMA request.
These are three ways to release DMA Idle mode:
1.
Execute a reset. It is the same that Idle mode.
2.
Any active interrupt happens, causing DMA Idle mode to be released. It is as same as IDLE mode.
3.
The external DMA request makes DMA Idle mode to be released and Acknowledge makes CPU in IDLE
mode.