Instruction Exceptions; Types Of Instruction Exceptions; Trap Instruction - Hitachi SH7032 Hardware Manual

4.5

Instruction Exceptions

4.5.1

Types of Instruction Exceptions

Table 4.8 shows the three types of instruction that start exception handling (trap instructions,
illegal slot instructions, and general illegal instructions).
Table 4.8 Types of Instruction Exceptions
Type Source Instruction

Trap instruction

TRAPA
Illegal slot Undefined code or instruction
instruction that rewrites the PC located
immediately after a delayed
branch instruction (delay slot)
General illegal Undefined code in other than
instructions delay slot
4.5.2 Trap Instruction
Trap instruction exception handling is carried out when a trap instruction (TRAPA) is executed.
The CPU then:
1. Saves the status register by pushing register contents onto the stack.
2. Pushes the program counter value onto the stack. The PC value saved is the start address of the
next instruction after the TRAPA instruction.
3. Reads the exception handling routine start address from the vector table corresponding to the
vector number specified in the TRAPA instruction, branches to that address, and starts
program execution. The branch is not a delayed branch.
Comments
—
Delayed branch instructions are: JMP, JSR,
BRA, BSR, RTS, RTE. Instructions that
rewrite the PC are: JMP, JSR, BRA, BSR,
RTS, RTE, BT, BF, and TRAPA
—
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