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Suppose the clock has interrupted the processor.
Both clock vector locations, 100 and 104, have the same information. PC is set to the address of the location labelled “kwlp” (0568) and PS is set to show:
present mode = kernel mode
previous mode = kernel or user mode
priority = 6
Note. The PS will contain the true previous mode, regardless of the value picked up from the vector location.
The vector location contains a new PC value which is the address of the statement labelled “kwlp”. This instruction is a subroutine call on “call” via r0.
After the execution of this instruction, r0 is left with the address of the code word after the instruction which contains “_clock”, i.e. r0 contains the address of the address of the “clock” routine in the file “clock.c” (3725).
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