Specifications
Related Information
Exception Processing on page 3-36
The ipending Register
The value of the ipending register indicates the value of the enabled interrupt signals driven into the
processor. A value of one in bit n means that the corresponding irq n input is asserted and enabled in the
ienable register. Writing a value to the ipending register has no effect.
Note: The ipending register is present only when the internal interrupt controller is implemented.
The cpuid Register
The cpuid register holds a constant value that you define in the Nios II Processor parameter editor to
uniquely identify each processor in a multiprocessor system. In Qsys, unique values must be assigned
manually. Writing to the cpuid register has no effect.
The exception Register
When the extra exception information option is enabled, the Nios II processor provides information
useful to system software for exception processing in the exception and badaddr registers when an
exception occurs. When your system contains an MMU or MPU, the extra exception information is
always enabled. When no MMU or MPU is present, the Nios II Processor parameter editor gives you the
option to have the processor provide the extra exception information.
For information about controlling the extra exception information option, refer to the Instantiating the
Nios II Processor chapter of the Nios II Processor Reference Handbook.
Table 3-12: exception Control Register Fields
Bit Fields
ECCFTL 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17
Reserved
16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Reserved Cause Rsvd
Table 3-13: exception Control Register Field Descriptions
Field Description Access Reset Available
ECCFTL The Nios II processor writes to ECCFTL when it detects a
potentially fatal ECC error. When ECCFTL = 1, the Nios II
processor detects an ECC register file error. When
ECCFTL = 0, another ECC exception occurred.
Read 0 Only
with
ECC
CAUSE CAUSE is written by the Nios II processor when certain
exceptions occur. CAUSE contains a code for the highest-
priority exception occurring at the time. The Cause
column in the Nios II Exceptions (In Decreasing Priority
Order table lists the CAUSE field value for each exception.
CAUSE is not written on a break or an external interrupt.
Read 0 Only
with
extra
exceptio
n
informa‐
tion
NII51003
2015.04.02
The ipending Register
3-17
Programming Model
Altera Corporation
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