upd70f3017ay Renesas Electronics Corporation., upd70f3017ay Datasheet - Page 128

• Manufacturer Part Number: upd70f3017ay
• Description: V850/sa1tm 32-/16-bit Single-chip Microcontroller
• Manufacturer: Renesas Electronics Corporation.

5.4.2 Restore
128
To restore or return execution from the software exception service routine, the RETI instruction is used.
(1) Restores 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.
Caution When the PSW.EP bit and the PSW.NP bit are changed by the LDSR instruction during the
Remark
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.
The processing of the RETI instruction is shown below.
software 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
immediately before the RETI instruction.
The solid line shows the CPU processing flow.
1
CHAPTER 5 INTERRUPT/EXCEPTION PROCESSING FUNCTION
Original processing restored
PC
PSW
RETI instruction
Figure 5-11. RETI Instruction Processing
PSW.EP
PSW.NP
0
0
EIPC
EIPSW
User’s Manual U12768EJ4V1UD
1
PC
PSW
FEPC
FEPSW