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INSTRUCTION SET S3C8245/P8245/C8249/P8249
6-40
EI — Enable Interrupts
EI
Operation: SYM (0) ← 1
An EI instruction sets bit zero of the system mode register, SYM.0 to "1". This allows interrupts to
be serviced as they occur (assuming they have highest priority). If an interrupt's pending bit was set
while interrupt processing was disabled (by executing a DI instruction), it will be serviced when you
execute the EI instruction.
Flags: No flags are affected.
Format:
Bytes Cycles Opcode
(Hex)
opc 1 4 9F
Example: Given: SYM = 00H:
EI
If the SYM register contains the value 00H, that is, if interrupts are currently disabled, the statement
"EI" sets the SYM register to 01H, enabling all interrupts. (SYM.0 is the enable bit for global
interrupt processing.)