CHAPTER 3 CP0 REGISTERS
User’s Manual U14272EJ3V0UM
77
Figure 3-12. Status Register (2/2)
KX:
Enables 64-bit addressing in Kernel mode (0
→
32-bit, 1
→
64-bit). 64-bit operations are always
valid in Kernel mode.
SX:
Enables 64-bit addressing and operation in Supervisor mode (0
→
32-bit, 1
→
64-bit).
UX:
Enables 64-bit addressing and operation in User mode (0
→
32-bit, 1
→
64-bit).
KSU:
Sets and indicates the operating mode (10
→
User, 01
→
Supervisor, 00
→
Kernel).
ERL:
Sets and indicates the error level (0
→
Normal, 1
→
Error).
EXL:
Sets and indicates the exception level (0
→
Normal, 1
→
Exception).
IE:
Sets and indicates interrupt enabling/disabling (0
→
Disabled, 1
→
Enabled).
0:
Reserved for future use. Write 0 in a write operation. When this bit is read, 0 is read.
Figure 3-13 shows the details of the Diagnostic Status (DS) field. All DS field bits other than the TS bit are
writable.
Figure 3-13. Status Register Diagnostic Status Field
16
17
18
19
20
21
22
23
24
0
BEV
TS
SR
0
CH
CE
DE
BEV:
Specifies the base address of a TLB Refill exception vector and common exception vector (0
→
Normal, 1
→
Bootstrap).
TS:
Occurs the TLB to be shut down (read-only) (0
→
Not shut down, 1
→
Shut down). This bit is used
to avoid any problems that may occur when multiple TLB entries match the same virtual address.
After the TLB has been shut down, reset the processor to enable restart. Note that the TLB is shut
down even if a TLB entry matching a virtual address is marked as being invalid (with the V bit
cleared).
SR:
Occurs a Soft Reset or NMI exception (0
→
Not occurred, 1
→
Occurred).
CH:
CP0 condition bit (0
→
False, 1
→
True). This bit can be read and written by software only; it
cannot be accessed by hardware.
CE, DE:
These are prepared to maintain compatibility with the V
R
4100, and are not used in the V
R
4181
hardware.
0:
Reserved for future use. Write 0 in a write operation. When this field is read, 0 is read.
The Status register has the following fields where the modes and access statuses are set.