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Section 4 Exception Handling
4.4
Interrupt Exception Handling
Interrupts are controlled by the interrupt controller. The sources to start interrupt exception
handling are external interrupt sources (NMI and IRQ15 to IRQ0) and internal interrupt sources
from the on-chip peripheral modules. NMI is an interrupt with the highest priority. For details, see
section 5, Interrupt Controller.
Interrupt exception handling is conducted as follows:
1. The values in the program counter (PC) and condition code register (CCR) are saved to the
stack.
2. A vector address corresponding to the interrupt source is generated, the start address is loaded
from the vector table to the PC, and program execution begins from that address.
4.5
Trap Instruction Exception Handling
Trap instruction exception handling starts when a TRAPA instruction is executed. Trap instruction
exception handling can be executed at all times in the program execution state.
Trap instruction exception handling is conducted as follows:
1. The values in the program counter (PC) and condition code register (CCR) are saved to the
stack.
2. A vector address corresponding to the interrupt source is generated, the start address is loaded
from the vector table to the PC, and program execution starts from that address.
The TRAPA instruction fetches a start address from a vector table entry corresponding to a vector
number from 0 to 3, as specified in the instruction code.
Table 4.3 shows the status of CCR after execution of trap instruction exception handling.
Table 4.3
Status of CCR after Trap Instruction Exception Handling
Interrupt Control Mode
0
1
Rev. 1.00 Mar. 12, 2008 Page 74 of 1178
REJ09B0403-0100
I
Set to 1
Set to 1
CCR
UI
Retains value prior to
execution
Set to 1
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