Eit (Exception, Interrupt, And Trap) - Fujitsu FR60 Hardware Manual

CHAPTER 3 CPU AND CONTROL UNITS
3.7

EIT (Exception, Interrupt, and Trap)

EIT, a generic term for exception, interrupt, and trap, refers to suspending program
execution if an event occurs during execution and then executing another program.
An exception is an event that occurs related to the execution context. Execution
restarts from the instruction that caused the exception.
An interrupt is an event that occurs independently of execution context. The event is
caused by hardware.
A trap is an event that occurs related to the execution context. Some traps, such as
system calls, are specified in a program. Execution restarts from the instruction
following the one that caused the trap.
■ Features of EIT
• Multiple interrupts support
• Level masking function (15 levels available to the user)
• Trap instruction (INT)
• Emulator activation EIT (hardware/software)
■ EIT Causes
The following are causes of EIT:
• Reset
• User interrupt (internal resource, external interrupt)
• NMI
• Delayed interrupt
• Undefined instruction exception
• Trap instruction (INT)
• Trap instruction (INTE)
• Step trace trap
• No-coprocessor trap
• Coprocessor error trap
Note:
Restrictions apply to EIT regarding the delay slot of branch instructions. See Section "3.6 Branch
Instructions" for more information.
■ Return from EIT
• RETI instruction
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