Enable/Disable Interrupt Instructions (Ei, Di); Interrupt Pending Function Types; Interrupt Priority - Samsung S3C9444 User Manual

8-bit cmos microcontrollers

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INTERRUPT STRUCTURE

ENABLE/DISABLE INTERRUPT INSTRUCTIONS (EI, DI)

The system mode register, SYM (DFH), is used to enable and disable interrupt processing.

SYM.2 is the enable and disable bit for global interrupt processing respectively, by modifying SYM.2. An Enable

Interrupt (EI) instruction must be included in the initialization routine that follows a reset operation in order to

enable interrupt processing. Although you can manipulate SYM.2 directly to enable and disable interrupts during

normal operation, we recommend that you use the EI and DI instructions for this purpose.

When the interrupt service routine has executed, the application program's service routine must clear the

appropriate pending bit before the return from interrupt subroutine (IRET) occurs.

Because there is not a interrupt priority register in SAM88RCRI, the order of service is determined by a sequence

of source which is executed in interrupt service routine.

"EI" Instruction

Execution

Source Interrupts

Source Interrupt

5-2

RESET

Enable

Figure 5-2. Interrupt Function Diagram

Interrupt Pending

Interrpt priority

is determind by

software polling

method

Global Interrupt

Control (EI, DI instruction)

S3C9444/F9444_UM_REV1.10

Vector Interrupt

Cycle

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