Restore - NEC V850/SA1 mPD703015 Preliminary User's Manual

5.4.2 Restore

To restore or return execution from the software exception service routine, the RETI instruction is used.
Operation of RETI instruction
When the RETI instruction is executed, the CPU performs the following steps, and transfers control to the address
of the restored PC.
(1) Restores the restored PC and PSW from EIPC and EIPSW because the EP bit of PSW is 1.
(2) Transfers control to the address of the restored PC and PSW.
Figure 5-14 illustrates the processing of the RETI instruction.
1
Caution When the PSW.EP bit and the PSW.NP bit are changed by the LDSR instruction during the soft-
ware exception process, 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 immedi-
ately before the RETI instruction.
Remark
The solid line shows the CPU processing flow.
CHAPTER 5 INTERRUPT/EXCEPTION PROCESSING FUNCTION
Figure 5-14. RETI Instruction Processing
RETI instruction
PSW.EP
0
PSW.NP
0
PC EIPC
PSW EIPSW
Original processing restored
1
PC FEPC
PSW FEPSW
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