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4.1.2
Exception Handling Operation
Exceptions originate from various sources. Trap instructions and interrupts are handled as follows:
1. The program counter (PC), condition code register (CCR), and extended register (EXR) are
pushed onto the stack.
2. The interrupt mask bits are updated. The T bit is cleared to 0.
3. A vector address corresponding to the exception source is generated, and program execution
starts from that address.
For a reset exception, steps 2 and 3 above are carried out.
4.1.3
Exception Vector Table
The exception sources are classified as shown in figure 4-1. Different vector addresses are
assigned to different exception sources.
Table 4-2 lists the exception sources and their vector addresses.
Exception
sources
80
Power-on reset
Reset
Manual reset
Trace
External interrupts: NMI, IRQ7 to IRQ0
Interrupts
Internal interrupts: 72 interrupt sources in
on-chip supporting modules
Trap instruction
Figure 4-1 Exception Sources
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