Samsung 8-Bit CMOS Microcontroller, S3C9228/P9228 user manual EI Enable Interrupts

S3C9228/P9228 SAM88RCRI INSTRUCTION SET

EI — Enable Interrupts

EI

Operation: SYM (2) ¨ 1

An EI instruction sets bit 2 of the system mode register, SYM.2 to "1". This allows interrupts to be serviced as they occur. 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 04H, enabling all interrupts (SYM.2 is the enable bit for global interrupt processing).

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