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Chapter 6 EIT: Exceptions, Interrupts and Traps
8.Operation
8.2 Operation of INT Instruction
INT No. u8 instruction is operated as follows.
Branches to interrupt handler of vector specified in u8.
■ Operation
1. The contents of the program status (PS) are saved to the system stack.
2. The address of the next instruction is saved to the system stack.
3. The value of the system stack pointer (SSP) is reduced by 8.
4. The value “0” is written to the “I” flag in the condition code register (CCR) in the program status (PS).
5. The value “0” is written to the “S” flag in the condition code register (CCR) in the program status (PS).
6. The value ‘TBR+3FC
H
-4 x u8’ is stored in the program counter (PC).
8.3 Operation of INTE Instruction
INTE instruction is operated as follows.
Branches to vector interrupt handler of vector number 9.
■ Operation
1. The contents of the program status (PS) are saved to the system stack.
2. The address of the next instruction is saved to the system stack.
3. The value of the system stack pointer (SSP) is reduced by 8.
4. The value (level) “4” is stored in the “ILM”.
5. The value “0” is written to the “S” flag in the condition code register (CCR) in the program status (PS).
6. The value ‘TBR+3D8
H
’ is stored in the program counter (PC).
During the execution of step, EIT is not generated by INTE.
Since INTE instruction is used for the device, do not use it.