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Section 9 Exception Handling
Rev. 4.00 Sep. 14, 2005 Page 200 of 982
REJ09B0023-0400
9.2
Exception Handling Function
9.2.1
Exception Handling Flow
In exception handling, the contents of the program counter (PC) and status register (SR) are saved
in the saved program counter (SPC) and saved status register (SSR), respectively, and execution of
the exception handler is invoked from a vector address. The return from exception handler (RTE)
instruction is issued by the exception handler routine on completion of the routine, restoring the
contents of PC and SR to return to the processor state at the point of interruption and the address
where the exception occurred.
A basic exception handling sequence consists of the following operations. If an exception occurs
and the CPU accepts it, operations 1 to 8 are executed.
1. The contents of PC is saved in SPC.
2. The contents of SR is saved in SSR.
3. The block (BL) bit in SR is set to 1, masking any subsequent exceptions.
4. The register bank (RB) bit in SR is set to 1.
5. An exception code identifying the exception event is written to bits 11 to 0 of the exception
event (EXPEVT) or interrupt event (INTEVT2) register.
6. If a TRAPA instruction is executed, an 8-bit immediate data specified by the TRAPA
instruction is set to TRA.
7. Instruction execution jumps to the designated exception vector address to invoke the handler
routine.
The above operations from 1 to 7 are executed in sequence. During these operations, no other
exceptions may be accepted unless multiple exception acceptance is enabled.
In an exception handling routine for a general exception, the appropriate exception handling must
be executed based on an exception source determined by the EXPEVP. In an interrupt exception
handling routine, the appropriate exception handling must be executed based on an exception
source determined by the INTEVT2. After the exception handling routine has been completed,
program execution can be resumed by executing an RTE instruction. The RTE instruction causes
the following operations to be executed.
1. The contents of the SSR are restored into the SR to return to the processing state in effect
before the exception handling took place.
2. A delay slot instruction of the RTE instruction is executed.
3. Control is passed to the address stored in the SPC.
Summary of Contents for HD6417641
Page 2: ...Rev 4 00 Sep 14 2005 Page ii of l...
Page 7: ...Rev 4 00 Sep 14 2005 Page vii of l...
Page 11: ...Rev 4 00 Sep 14 2005 Page xi of l USB Universal serial bus WDT Watch dog timer...
Page 12: ...Rev 4 00 Sep 14 2005 Page xii of l...
Page 28: ...Rev 4 00 Sep 14 2005 Page xxviii of l...
Page 204: ...Section 4 Clock Pulse Generator CPG Rev 4 00 Sep 14 2005 Page 154 of 982 REJ09B0023 0400...
Page 212: ...Section 5 Watchdog Timer WDT Rev 4 00 Sep 14 2005 Page 162 of 982 REJ09B0023 0400...
Page 228: ...Section 6 Power Down Modes Rev 4 00 Sep 14 2005 Page 178 of 982 REJ09B0023 0400...
Page 246: ...Section 8 X Y Memory Rev 4 00 Sep 14 2005 Page 196 of 982 REJ09B0023 0400...
Page 318: ...Section 11 User Break Controller UBC Rev 4 00 Sep 14 2005 Page 268 of 982 REJ09B0023 0400...
Page 454: ...Section 12 Bus State Controller BSC Rev 4 00 Sep 14 2005 Page 404 of 982 REJ09B0023 0400...
Page 504: ...Section 14 U Memory Rev 4 00 Sep 14 2005 Page 454 of 982 REJ09B0023 0400...
Page 566: ...Section 17 Compare Match Timer CMT Rev 4 00 Sep 14 2005 Page 516 of 982 REJ09B0023 0400...
Page 868: ...Section 21 A D Converter Rev 4 00 Sep 14 2005 Page 818 of 982 REJ09B0023 0400...
Page 914: ...Section 23 I O Ports Rev 4 00 Sep 14 2005 Page 864 of 982 REJ09B0023 0400...
Page 956: ...Section 24 List of Registers Rev 4 00 Sep 14 2005 Page 906 of 982 REJ09B0023 0400...
Page 1016: ...Section 25 Electrical Characteristics Rev 4 00 Sep 14 2005 Page 966 of 982 REJ09B0023 0400...
Page 1024: ...Appendix Rev 4 00 Sep 14 2005 Page 974 of 982 REJ09B0023 0400...
Page 1032: ...Rev 4 00 Sep 14 2005 Page 982 of 982 REJ09B0023 0400 X X Y data addressing 52 X Y memory 193...
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