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IDT MIPS32 4Kc Processor Core
CP0 Registers
79RC32438 User Reference Manual
2 - 73
November 4, 2002
Notes
address references for which the ASID value in the WatchHi register matches the ASID value in the EntryHi
register cause a watch exception. The optional mask field provides address masking to qualify the address
specified in WatchLo.
WatchHi Register Format
31 30 29
Debug Register (CP0 Register 23)
The Debug register is used to control the debug exception and provide information about the cause of
the debug exception and when re-entering at the debug exception vector due to a normal exception in
debug mode. The read-only information bits are updated every time the debug exception is taken or when a
normal exception is taken when already in debug mode.
Only the DM bit and the EJTAGver field are valid when read from non-debug mode; the value of all other
bits and fields is UNPREDICTABLE. Operation of the processor is UNDEFINED if the Debug register is
written from non-debug mode.
Some of the bits and fields are only updated on debug exceptions and/or exceptions in debug mode, as
shown below:
–
DSS, DBp, DDBL, DDBS, DIB, DINT are updated on both debug exceptions and on exceptions in
debug modes
–
DExcCode is updated on exceptions in debug mode, and is undefined after a debug exception
–
Halt and Doze are updated on a debug exception, and is undefined after an exception in debug
mode
–
DBD is updated on both debug and on exceptions in debug modes.
All bits and fields are undefined when read from normal mode, except those explicitly described to be
defined, such as EJTAGver and DM.
Debug Register Format
31
24 23
16 15
12 11
3 2
0
0 G
0
ASID
0
MASK
0
Fields
Description
Read/
Write
Reset
State
Name
Bit(s)
0
31
Must be written as zero; returns zero on read.
0
0
G
30
If this bit is one, any address that matches that spec-
ified in the
WatchLo
register causes a watch excep-
tion. If this bit is zero, the ASID field of the
WatchHi
register must match the ASID field of the
EntryHi
reg-
ister to cause a watch exception.
R/W
Undefined
0
29:24
Must be written as zero; returns zero on read.
0
0
ASID
23:16
ASID value which is required to match that in the
EntryHi
register if the G bit is zero in the
WatchHi
register.
R/W
Undefined
Table 2.49 WatchHi Register Field Descriptions
30
29
28
27
26
25
24
23 22
21
20
19 18
DBD DM
R
LSNM Doze Halt
CountDM IBusEP
R
DBusEP
IEXI
R
17
15 14
10
9
8
7
6
5
4
3
2
1
0
Ver
DExcCode
R
SSt
R
DINT DIB DDBS DDBL DBp DSS