Nios II Classic Processor Reference Guide

ID 683620
Date 10/28/2016
Document Table of Contents The badaddr 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 this document.

When the option for extra exception information is enabled and a processor exception occurs, the badaddr register contains the byte instruction or data address associated with certain exceptions at the time the exception occurred. The Nios® II Exceptions Table lists which exceptions write the badaddr register along with the value written.

Table 25.  badaddr Control Register Fields
Bit Fields
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Table 26.  badaddr Control Register Field Descriptions
Field Description Access Reset Available
BADDR BADDR contains the byte instruction address or data address associated with an exception when certain exceptions occur. The Address column of the Nios® II Exceptions Table lists which exceptions write the BADDR field. Read 0 Only with extra exception information

The BADDR field allows up to a 32-bit instruction address or data address. If an MMU or MPU is present, the BADDR field is 32 bits because MMU and MPU instruction and data addresses are always full 32-bit values. When an MMU is present, the BADDR field contains the virtual address.

If there is no MMU or MPU and the Nios II address space is less than 32 bits, unused high-order bits are written and read as zero. If there is no MMU, bit 31 of a data address (used to bypass the data cache) is always zero in the BADDR field.