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CHAPTER 2 CPU
2.8
EIT (Exception, Interrupt, and Trap)
EIT indicates that the program being executed is interrupted by an event and another
program is executed. EIT is a generic name coined from the words: exception,
interrupt, and trap.
An exception is an event that occurs in connection with the context of the current
execution. Program execution resumes from the instruction that has caused an
exception.
An interrupt is an event that occurs regardless of the context of the current execution.
The event is caused by hardware.
A trap is an event that occurs in connection with the context of the current execution.
Some traps such as a system call are indicated by a program. Execution resumes
from the instruction following the one that caused a trap.
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EIT Characteristics
•
Support of multiple concurrent interrupts
•
Interrupt level mask function (The user can use 15 levels.)
•
Trap instruction (INT)
•
EIT for emulator activation (hardware and software)
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EIT Causes
The EIT causes are as follows:
•
Reset
•
User interrupt (internal resource, external interrupt)
•
NMI
•
Delayed interrupt
•
Undefined-instruction exception
•
Trap instruction (INT)
•
Trap instruction (INTE)
•
Step-trace-trap
•
Coprocessor nonexistent trap
•
Coprocessor error trap
■
Return from EIT
Use the following instruction to return from EIT:
•
RETI instruction
Summary of Contents for MB91F109
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Page 96: ...72 CHAPTER 2 CPU ...
Page 224: ...200 CHAPTER 4 BUS INTERFACE ...
Page 234: ...210 CHAPTER 5 I O PORTS ...
Page 268: ...244 CHAPTER 9 U TIMER ...
Page 290: ...266 CHAPTER 10 UART ...
Page 314: ...290 CHAPTER 12 16 BIT RELOAD TIMER ...
Page 322: ...298 CHAPTER 13 BIT SEARCH MODULE ...
Page 392: ...368 CHAPTER 16 FLASH MEMORY ...
Page 432: ...408 APPENDIX E Instructions F Table E 2 Instruction Formats OP rel11 5 11 ...
Page 448: ...424 APPENDIX E Instructions ...
Page 449: ...425 INDEX INDEX The index follows on the next page This is listed in alphabetic order ...
Page 458: ...434 INDEX ...
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