CHAPTER 7 INTERRUPT/EXCEPTION PROCESSING FUNCTION
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User’s Manual U15195EJ5V0UD
7.4.2 Restore
Returning from software exception processing is carried out by the RETI instruction.
By executing the RETI instruction, the CPU carries out the following processing and shifts control to the restored
PC’s address.
(1) Loads the restored PC and PSW from EIPC and EIPSW because the EP bit of the PSW is 1.
(2) Transfers control to the address of the restored PC and PSW.
Figure 7-9 illustrates the processing of the RETI instruction.
Figure 7-9. RETI Instruction Processing
PSW.EP
RETI instruction
PC
PSW
EIPC
EIPSW
PSW.NP
Original processing restored
PC
PSW
FEPC
FEPSW
1
1
0
0
Caution When the PSW.EP bit and the PSW.NP bit are changed by the LDSR instruction during the
software exception processing, in order to restore the PC and PSW correctly during
recovery by the RETI instruction, it is necessary to set PSW.EP back to 1 using the LDSR
instruction immediately before the RETI instruction.
Remark
The solid lines show the CPU processing flow.