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27.3
Precautions in Usage
Address trap interrupt arises 2 states after prefetching the trap address. Trap interrupt may occur
after the trap instruction has been executed, depending on a combination of instructions
immediately preceding the setting up of the address trap.
If the instruction to trap immediately follows the branch instruction or the conditional branch
instruction, operation may differ, depending on whether the condition was satisfied or not, or the
address to be stacked may be located at the branch. Figures 27.2 to 27.22 show specific
operations.
For information as to where the next instruction prefetch occurs during the execution cycle of
the instruction, see appendix A.5 of this manual or section 2.7 Bus State during Execution of
Instruction of the H8S/2600, H8S/2000 Series Programming Manual. (R:W NEXT is the next
instruction prefetch.)
27.3.1
Basic Operations
After terminating the execution of the instruction being executed in the second state from the
trap address prefetch, the address trap interrupt exception handling is started.
(1) Figure 27.2 shows the operation when the instruction immediately preceding the trap address
is that of 3 states or more of the execution cycle and the next instruction prefetch occurs in
the state before the last 2 states. The address to be stacked is 0260.
MOV
instruc-
tion
pre-fetch
Address bus
025E
Interrupt
request
signal
Note: In the figure above, the NOP instruction is used as the typical example of instruction
with execution cycle of 1 state. Other instructions with the execution cycle of 1 state
also apply (Ex. MOV.B, Rs, Rd).
Internal
Data
NOP
Start of exception
opera-
read
instruc-
handling
tion
tion
pre-fetch
0260
0000
MOV
execution
Figure 27.2 Basic Operations (1)
Immediately
preceding
Instruction
0262
Rev. 2.0, 11/00, page 595 of 1037
(ER3 = H'0000)
Address
025E
MOV.B @ER3+,R2L
*
0260
NOP
0262
NOP
0264
NOP
* Trap setting address
The underlines address is the
one to be actually stacked.
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