Specifications
The WR Flag
Setting the WR flag signifies that an MPU region write operation should be performed when a wrctl
instruction is issued to the mpuacc register. Refer to the MPU Region Read and Write Operations section
for more information. The WR flag always returns 0 when read by a rdctl instruction.
Note: Setting both the RD and WR flags to one results in undefined behavior.
Related Information
MPU Region Read and Write Operations on page 3-32
The eccinj Register
The eccinj register injects 1 and 2 bit errors to the Nios II processor’s internal RAM blocks that support
ECC. Injecting errors allows the software to test the ECC error exception handling code. The error(s) are
injected in the data bits, not the parity bits. The eccinj register is only available when ECC is present.
Table 3-32: eccinj Control Register Fields
Bit Fields
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16
Reserved
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Reserved TLB Reserved ICDAT ICTAG RF
Software writes 0x1 to inject a 1 bit ECC error or 0x2 to inject a 2-bit ECC error to the RAM field.
Hardware sets the value of the inject field to 0x0 after the error injection has occurred.
Table 3-33: eccinj Control Register Field Descriptions
Field Description Access Reset Available
RF Inject an ECC error in the register file’s RAM. Read/
Write
0 Only with ECC
ICTAG Inject an ECC error in the instruction cache Tag RAM. Read/
Write
0 Only with ECC
ICDAT Inject an ECC error in the instruction cache data RAM. Read/
Write
0 Only with ECC
TLB Inject an ECC error in the MMU TLB RAM. Errors are
injected in the tag portion of the VPN field.
Read/
Write
0 Only with ECC
Refer to “Working with ECC” for more information about when errors are injected.
Related Information
Working with ECC on page 3-34
Shadow Register Sets
The Nios II processor can optionally have one or more shadow register sets. A shadow register set is a
complete alternate set of Nios II general-purpose registers, which can be used to maintain a separate
runtime context for an interrupt service routine (ISR).
NII51003
2015.04.02
The WR Flag
3-29
Programming Model
Altera Corporation
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