KS57C2308/P2308/C2316/P2316 SAM47 INSTRUCTION SET
5-53
IDLE — Idle Operation
IDLE
Operation: Operand Operation Summary Bytes Cycles
–Engage CPU idle mode 2 2
Description: IDLE causes the CPU clock to stop while the system clock continues oscillating by setting bit 2 of
the power control register (PCON). After an IDLE instruction has been executed, peripheral
hardware remains operative.
In application programs, an IDLE instruction must be immediately followed by at least three NOP
instructions. This ensures an adequate time interval for the clock to stabilize before the next
instruction is executed. If more than three NOP instructions are not used after IDLE instruction,
leakage current could be flown because of the floating state in the internal bus.
Operand Binary Code Operation Notation
– 11111111PCON.2 ← 1
10100011
Example: The instruction sequence
IDLE
NOP
NOP
NOP
sets bit 2 of the PCON register to logic one, stopping the CPU clock. The three NOP instructions
provide the necessary timing delay for clock stabilization before the next instruction in the
program sequence is executed.