Saving And Restoring The Pc And Psw - Mitsubishi Electric M32R Series User Manual

Mitsubishi 32-bit risc single-chip microcomputers

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4.6 Saving and Restoring the PC and PSW

The following describes operation of the M32R at the time when it accepts an EIT and when it

executes the "RTE" instruction.

(1) Hardware preprocessing when an EIT is accepted

Save the SM, IE, and C bits of the PSW register

Update the SM, IE, and C bits of the PSW register

Save the PC register

Set the vector address in the PC register

Branches to the EIT vector and executes the branch instruction ("BRA" instruction) written

in it, thereby transferring control to the user-created EIT handler.

(2) Hardware postprocessing when the "RTE" instruction is executed

Restore the SM, IE, and C bits of the PSW register from their backup bits.

Restore the value of the PC register from the BPC register

Note: The value of the BPC register and those of the BSM, BIE, and BC bits of the PSW register

after execution of the "RTE" instruction are indeterminate.

← Remains unchanged (RIE, AE, TRAP)

or set to 0 (SBI, EI, RI)

4.6 Saving and Restoring the PC and PSW