Control Registers - Intel NIOS II Owner Reference Manual

Register Name
r6
r7
r8
r9
r10
r11
r12
r13
r14
r15
Note:
is used exclusively by the JTAG debug module. It is used as the breakpoint
r25
temporary (
reserved.
Note:
is used as the breakpoint return address (
r30
the shadow register set status (
about
sstatus
For more information, refer to the Application Binary Interface chapter of the Nios II
Processor Reference Handbook.
Related Information
Application Binary Interface

3.4.2. Control Registers

Control registers report the status and change the behavior of the processor. Control
registers are accessed differently than the general-purpose registers. The special
instructions
registers and are only available in supervisor mode.
Note: When writing to control registers, all undefined bits must be written as zero.
The Nios II architecture supports up to 32 control registers. All nonreserved control
registers have names recognized by the assembler.
Table 12. Control Register Names and Bits
Register
0
1
2
3
Nios II Processor Reference Guide
46
Function
Register arguments
Register arguments
Caller-saved register
Caller-saved register
Caller-saved register
Caller-saved register
Caller-saved register
Caller-saved register
Caller-saved register
Caller-saved register
) register in the normal register set. In shadow register sets,
bt
sstatus
, refer to The Status Register section.
on page 146
and provide the only means to read and write to the control
rdctl wrctl
Name
status
estatus
bstatus
ienable
Register Name
r22
r23
r24 et
r25 bt
r26 gp
r27 sp
r28 fp
r29 ea
r30 sstatus
r31 ra
) in the normal register set, and as
ba
) in each shadow register set. For details
Register Contents
Refer to The status Register on page 48
Refer to The estatus Register
Refer to The bstatus Register
Internal interrupt-enable bits
The ienable Register
3. Programming Model
NII-PRG | 2018.04.18
Function
Callee-saved register
Callee-saved register
Exception temporary
Breakpoint temporary
Global pointer
Stack pointer
Frame pointer
Exception return address
Status register
Return address
is
r25
on page 50
continued...