User’s Manual
C166S V1 SubSystem
Central Processing Unit
User’s Manual
3-31
V 1.6, 2001-08
During the execution of a Class A trap service routine, any Class B trap will not be
serviced until the Class A trap service routine is exited with a RETI instruction. In this
case, the Class B trap condition is stored in the TFR but the IP value of the instruction
that caused this trap will be lost.
UNDefined OPCode Trap (UNDOPC)
When the instruction currently decoded by the CPU does not contain a valid C166S
opcode, the UNDOPC flag is set in the TFR, and the CPU enters the undefined opcode
trap routine. The IP value pushed onto the system stack is the address of the instruction
that caused the trap.
This can be used to emulate unimplemented instructions. The trap service routine can
examine the faulting instruction to decode operands for unimplemented opcodes based
on the stacked IP. In order to resume processing, the stacked IP value must be
incremented by the size of the undefined instruction, which is determined by the user,
before a RETI instruction is executed.
PRoTection FauLT Trap (PRTFLT)
DISWDT, EINIT, IDLE, PWRDN, SRST, and SRVWDT are protected instructions.
Whenever one protected instruction is executed and the protection is broken, the
PRTFLT flag in register TFR is set and the CPU enters the protection fault trap routine.
The IP value pushed onto the system stack for the protection fault trap is the address of
the instruction that caused the trap.
ILLegal word OPerand Access Trap (ILLOPA)
Whenever a word operand read or write access is attempted to an odd byte address, the
ILLOPA flag in register TFR is set, and the CPU enters the illegal word operand access
trap routine. The IP value pushed onto the system stack is the address of the instruction
following the one that caused the trap.
ILLegal INstruction Access Trap (ILLINA)
Whenever a branch is made to an odd byte address, the ILLINA flag in register TFR is
set and the CPU enters the illegal instruction access trap routine. The IP value pushed
onto the system stack is the illegal odd target address of the branch instruction.
ILLegal external BUS access Trap (ILLBUS)
Whenever the CPU requests an external instruction fetch or a data read or a data write,
and no external bus configuration has been specified, the ILLBUS flag in register TFR is
set and the CPU enters the illegal bus access trap routine. The IP value pushed onto the
system stack is the address of the instruction following the one that caused the trap.
Содержание C166S V1 SubSystem
Страница 10: ...User s Manual C166S V1 SubSystem User s Manual I 6 V 1 6 2001 08...
Страница 16: ...User s Manual C166S V1 SubSystem Introduction User s Manual 1 6 V 1 6 2001 08...
Страница 126: ...User s Manual C166S V1 SubSystem Central Processing Unit User s Manual 3 96 V 1 6 2001 08...
Страница 178: ...User s Manual C166S V1 SubSystem Memory Organization User s Manual 4 52 V 1 6 2001 08...
Страница 206: ...User s Manual C166S V1 SubSystem Instruction Set User s Manual 5 28 V 1 6 2001 08...
Страница 306: ...User s Manual C166S V1 SubSystem Detailed Instruction Set User s Manual 6 100 V 1 6 2001 08...
Страница 362: ...User s Manual C166S V1 SubSystem The External Bus Interface User s Manual 8 40 V 1 6 2001 08...
Страница 452: ...User s Manual C166S V1 SubSystem General Purpose Timer Unit User s Manual 12 44 V 1 6 2001 08...
Страница 454: ...User s Manual C166S V1 SubSystem Instruction Index User s Manual 13 2 V 1 6 2001 08...
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