Multiple Eit Processing - Fujitsu MB91460 SERIES FR60 User Manual

7. Multiple EIT Processing

If multiple EITs are generated at the same time, CPU repeats the operation which selects one of the EIT to
accept, and then executes EIT sequence, and detects EIT again. If there is no EIT to accept upon detecting
EIT, CPU executes instruction of the last accepted EIT handler. Therefore, if multiple EITs are generated at
the same time, execution sequence of each EIT handler is determined by the following two parameters.
■ Priority Level of Receipt of EIT Triggers
Priority level of receipt of EIT triggers means the sequence to select which EIT triggers to execute by saving
PS and PC in order to update PC and masking other triggers where appropriate.
EIT does not always mean first-in first-out handler.
Table 7-1 Priority Level of Receipt of EIT Triggers and Mask for Other Triggers
Priority for accepting EITs
1
2
3
4
5
6
7
8
9
10
11
■ How to Mask Other Triggers upon the Receipt
Table below shows the execution sequence of each handler for multiple EIT triggers generated at the same
time when considering mask processes for other triggers upon the receipt of EIT triggers.
Table 7-2 Execution Sequence of EIT Handlers
Handler execution Priority
1
2
3
4
5
6
7
8
9
10
11
EIT
Reset
Instruction Break
INTE instruction
Undefined instruction exception
INT instruction / Coprocessor exceptions I-flag = 0
Memory protection violation
User interrupt
NMI (user)
NMI (emulator)
Step Trace trap
Operand Break
EIT
Reset
Undefined instruction exception
Instruction Break
INTE instruction
NMI (emulator)
Step Trace trap
Operand Break
NMI (user)
Memory protection violation
INT instruction / Coprocessor exceptions I-flag = 0
User interrupt
Chapter 6 EIT: Exceptions, Interrupts and Traps
7.Multiple EIT Processing
Masking of other EITs
All EITs are cleared
Other EITs are canceled (ILM = 4)
Other EITs are canceled (ILM = 4)
Other EITs are canceled (I-flag = 0)
I-flag = 0
ILM = level of accepted INT
ILM = 15
Other EITs are canceled (ILM = 4)
Other EITs are canceled (ILM = 4)
Other EITs are canceled (ILM = 4)
Masking of other EITs
All EITs are cleared
Other EITs are canceled (I-flag = 0)
Other EITs are canceled (ILM = 4)
Other EITs are canceled (ILM = 4)
Other EITs are canceled (ILM = 4)
Other EITs are canceled (ILM = 4)
Other EITs are canceled (ILM = 4)
ILM = 15
I-flag = 0
ILM = level of accepted INT
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