Exception Processing; Reserved Instruction Exception (Rie) - Mitsubishi Electric M32R Series User Manual

Mitsubishi 32-bit risc single-chip microcomputers

Table of Contents

4.8 Exception Processing

[Occurrence Conditions]

Reserved Instruction Exception (RIE) is generated when execution of a reserved instruction

(unimplemented instruction) is detected. Instruction check is performed on the op-code part of

the instruction.

When a reserved instruction exception occurs, the instruction which generated it is not executed.

If an external interrupt is requested at the same time a reserved instruction exception is detected,

it is the reserved instruction exception that is accepted.

[EIT Processing]

(1) Saving SM, IE, and C bits

The SM, IE, and C bits of the PSW register are saved to their backup bits – the BSM, BIE,

and BC bits.

(2) Updating SM, IE, and C bits

The SM, IE, and C bits of the PSW register are updated as shown below.

(3) Saving PC

The PC value of the instruction that generated the reserved instruction exception is set in

the BPC register. For example, if the instruction that generated the reserved instruction

exception is at address 4, the value 4 is set in the BPC register. Similarly, if the instruction

is at address 6, the value 6 is set in the BPC register. In this case, the value of the BPC

exception resides on a word boundary (BPC[30] = 0) or not on a word boundary (BPC[30]

However, in either case of the above, the address to which the "RTE" instruction returns

after completion of processing by the EIT handler is address 4. (This is because the two

low-order bits are cleared to "00" when returning to the PC.)

4.8 Exception Processing