Mitsubishi Electric M32R Series User Manual page 93

Mitsubishi 32-bit risc single-chip microcomputers

Table of Contents

4.3 EIT Processing Procedure

When an EIT is accepted, the M32R/E saves the PC and PSW (as will be described later) and

branches to the EIT vector. The EIT vector has an entry address assigned for each EIT. This is

where the BRA (branch) instruction (note that these are not branch address) for the EIT handler is

In the M32R/E's hardware preprocessing, only the contents of the PC and PSW registers are

transferred to the backup registers (BPC register and the BPSW field of the PSW register), and no

other operations are performed. Therefore, please make sure the BPC register, the PSW register

(including the BPSW field), and the general-purpose registers to be used in the EIT handler are

saved to the stack by the EIT handler you write. (Remember that these registers must be saved to

the stack in a program by the user.)

When processing by the EIT handler is completed, restore the saved registers from the stack and

finally execute the "RTE" instruction. Control is thereby returned from EIT processing to the

program that was being executed when the EIT occurred. (This does not apply to the System Break

Interrupt, however.)

In the M32R/E's hardware postprocessing, the contents of the backup registers (BPC register and

the BPSW field of the PSW register) are moved back to the PC and PSW registers.