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S3C8245/P8245/C8249/P8249 INSTRUCTION SET
6-87
WFI — Wait for Interrupt
WFI
Operation:
The CPU is effectively halted until an interrupt occurs, except that DMA transfers can still take
place during this wait state. The WFI status can be released by an internal interrupt, including a fast
interrupt .
Flags: No flags are affected.
Format:
Bytes Cycles Opcode
(Hex)
opc 1 4n 3F
( n = 1, 2, 3, … )
Example: The following sample program structure shows the sequence of operations that follow a "WFI"
statement:
EI
WFI
(Next instruction)
Main program
.
.
.
.
.
.
Interrupt occurs
Interrupt service routine
.
.
.
Clear interrupt flag
IRET
Service routine completed
(Enable global interrupt)
(Wait for interrupt)