nRESET and POWER-DOWN S3C8245/P8245/C8249/P8249
8-6
IDLE MODE
Idle mode is invoked by the instruction IDLE (opcode 6FH). In idle mode, CPU operations are halted while some
peripherals remain active. During idle mode, the internal clock signal is gated away from the CPU, but all peripherals
timers remain active. Port pins retain the mode (input or output) they had at the time idle mode was entered.
There are two ways to release idle mode:
1. Execute a reset. All system and peripheral control registers are reset to their default values and the contents of
all data registers are retained. The reset automatically selects the slow clock fxx/16 because CLKCON.4 and
CLKCON.3 are cleared to ‘00B’. If interrupts are masked, a reset is the only way to release idle mode.
2. Activate any enabled interrupt, causing idle mode to be released. When you use an interrupt to release idle
mode, the CLKCON.4 and CLKCON.3 register values remain unchanged, and the currently selected clock value
is used. The interrupt is then serviced. When the return-from-interrupt (IRET) occurs, the instruction immediately
following the one that initiated idle mode is executed.