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3.9.4 Multiple EIT Processing
When a number of EIT factors are generated simultaneously, one of the EIT factors is
selected and accepted in the CPU, and after the EIT sequence is executed, such EIT
factors are detected again. This operation is repeated as necessary.
When EIT factors are detected, if there are no more EIT factors that can be accepted, the
handler command for the last EIT factor accepted will be executed.
Therefore, the handler order for each factor when a number of EIT factors are generated
simultaneously is determined by the following two elements.
• Priority level of EIT factor acceptance
• How to mask the other factor at receiving
■ Priority Level of EIT Factor Acceptance
Priority for acceptance of the EIT factors indicates the order when selecting the factors executing the EIT
sequence that saves PS and PC, updates the PC (on demand) and performs mask processing of other
factors. The handler of the factor previously accepted is not always executed first.
Table 3.9-3 shows the priority level of the EIT factor acceptance.
A tinge of mask processing onto other factors after accepting the EIT factors is added, and each handling
procedure for the generated EIT factors are also mentioned in Table 3.9-4 .
Table 3.9-3 Priority level of EIT factor acceptance and masking other factor
Priority order
of acceptance
Factor Masking of other factor
1 Reset Other factors are abandoned.
2 Undefined instruction exception Cancellation
3
INT Instruction I Flag=0
Coprocessor absent trap
None
Coprocessor error trap
4 User Interrupt ILM = Level of accepted factor
5 NMI (for user) ILM=15
7 INTE Instruction ILM=4
8 Step trace trap ILM=4