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370 FUJITSU MICROELECTRONICS LIMITED CM71-00105-1E
CHAPTER 7 DETAILED EXECUTION INSTRUCTIONS
7.145
7.145 RETI (Return from Interrupt)
Loads data from the stack indicated by system stack pointer (SSP), to the program
counter (PC) and program status (PS), and retakes control from the EIT operation
handler.
● Assembler Format
RETI
● Operation
• Normal operation state
(SSP) → PC
SSP+4 → SSP
(SSP) → PS
SSP+4 → SSP
• Debug state
PC save register (PCSR) → PC
PS save register (PSSR) → PS
(PC) instruction execution
This is a privilege instruction, which is only available in privilege mode. If this instruction is executed in
user mode, it generates an invalid instruction exception (privilege instruction execution).
Operation varies depending on whether this instruction is executed in the normal operation state or debug
state. If this instruction is executed in the debug state, the DSU register is used instead of a stack, and the
acceptance of interrupts is withheld until the next instruction execution is completed. This, therefore,
executes one instruction necessarily after the RETI instruction was executed in the debug state.
At the time this instruction is executed, if the value of the interrupt level mask register (ILM) is in the range
16 to 31, only new ILM settings between 16 and 31 can be entered. If data in the range 0 to 15 is loaded in
memory, the value 16 will be added to that data before being transferred to the ILM. If the original ILM
value is in the range 0 to 15, then any value between 0 and 31 can be transferred to the ILM.
● Flag Change
D2, D1, S, I, N, Z, V, C: Change according to the values retrieved from the stack.
SINZVC
CCCCCC