HD6417615 Hitachi Semiconductor, HD6417615 Datasheet - Page 154

• Manufacturer Part Number: HD6417615
• Description: Hardware Manual
• Manufacturer: Hitachi Semiconductor

4.5.3
An instruction placed immediately after a delayed branch instruction is said to be placed in a delay
slot. If the instruction placed in the delay slot is undefined code, illegal slot exception handling
begins when the undefined code is decoded. Illegal slot exception handling is also started when an
instruction that rewrites the program counter (PC) is placed in a delay slot. The exception handling
starts when the instruction is decoded. The CPU handles an illegal slot instruction as follows:
1. The status register (SR) is saved to the stack.
2. The program counter (PC) is saved to the stack. The PC value saved is the jump address of the
3. The exception service routine start address is fetched from the exception vector table entry that
4.5.4
When undefined code placed anywhere other than immediately after a delayed branch instruction
(i.e., in a delay slot) is decoded, general illegal instruction exception handling starts. The CPU
handles general illegal instructions in the same way as illegal slot instructions. Unlike processing
of illegal slot instructions, however, the program counter value saved is the start address of the
undefined code.
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delayed branch instruction immediately before the undefined code or the instruction that
rewrites the PC.
corresponds to the exception that occurred. That address is jumped to and the program starts
executing. The jump that occurs is not a delayed branch.
Illegal Slot Instructions
General Illegal Instructions