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CM71-00105-1E FUJITSU MICROELECTRONICS LIMITED 61
FR81 Family
CHAPTER 4 RESET AND "EIT" PROCESSING
4.7
4.7.2 Priority Levels of EIT Requests
The sequence of accepting each request and executing the corresponding processing routines when multiple
EIT request occur simultaneously, is decided by two factors - by the priority levels of EIT requests, and,
how other EIT requests are to be masked when one EIT request has been accepted.
At the time when an EIT request occurs, and at the time of completion of an EIT sequence, the detection of
EIT requests being generated at that time is performed, and which EIT request will be accepted will be
decided. At the time of completion of the EIT sequence, the detection of EIT requests is carried out under
the condition where masking has been done for the EIT sources other than the EIT request accepted just a
while back. Table 4.7-1 shows the priority levels of EIT requests and masking of other sources.
There are times when the value of interrupt level mask register (ILM) gets modified due to the EIT request
accepted earlier and the other EIT sources occurring simultaneously get masked and cannot be accepted. In
such a case, until the processing routine of EIT sources that have occurred simultaneously have been
executed and the control has returned to the user program, the user interrupt is suspended and is re-detected
at the time of resumption of the user program.
Table 4.7-1 Priority Levels of EIT Requests & Masking of Other Sources
Priority level EIT Source Masking of other sources ILM after
updated
1 Reset Other sources discarded 15
2
Instruction break
Guarded access break
All factors given lower priority 4
3
Invalid instruction exception
Instruction access protection
exception
Data access protection exception
FPU exception
All factors given lower priority -
4 INT instruction I flag = 0
5 INTE instruction All factors given lower priority 4
6 General interrupt ILM= level of source accepted ICR
7 NMI ILM=15 15
8 Data access error interrupt - -
9 Break interrupt All factors given lower priority Request level
10 Step Trace Traps All factors given lower priority 4