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IDT MIPS32 4Kc Processor Core
CP0 Registers
79RC32438 User Reference Manual
2 - 74
November 4, 2002
Notes
Fields
Description
Read/
Write
Reset
State
Name
Bit(s)
DBD
31
Indicates whether the last debug exception or excep-
tion in debug mode, occurred in a branch delay slot:
0: Not in delay slot
1: In delay slot
R
Undefined
DM
30
Indicates that the processor is operating in debug
mode:
0: Processor is operating in non-debug mode
1: Processor is operating in debug mode
R
0
R
29
Reserved. Must be written as zero; returns zero on
read.
R
0
LSNM
28
Controls access of load/store between dseg and
main memory:
0: Load/stores in dseg address range goes to dseg.
1: Load/stores in dseg address range goes to main
memory.
R/W
0
Doze
27
Indicates that the processor was in any kind of low
power mode when a debug exception occurred:
0: Processor not in low power mode when debug
exception occurred
1: Processor in low power mode when debug excep-
tion occurred
R
Undefined
Halt
26
Indicates that the internal system bus clock was
stopped when the debug exception occurred:
0: Internal system bus clock stopped
1: Internal system bus clock running
R
Undefined
CountDM
25
Indicates the Count register behavior in debug mode.
Encoding of the bit is:
0: Count register stopped in debug mode
1: Count register increments in debug mode
R/W
1
IBusEP
24
Instruction fetch Bus Error exception Pending. Set
when an instruction fetch bus error event occurs or if
a 1 is written to the bit by software. Cleared when a
Bus Error Exception on Instruction Fetch is taken by
the processor, and by reset. If IBusEP is set when
IEXI is cleared, a Bus Error exception on instruction
fetch is taken by the processor, and IBusEP is
cleared.
R/W1
0
R
23:22
Reserved. Must be written as zero; returns zero on
read.
R
0
DBusEP
21
Data access Bus Error exception Pending. Covers
imprecise bus errors on data access, similar to
behavior of IBusEP for imprecise bus errors on an
instruction fetch.
R/W1
0
Table 2.50 Debug Register Field Descriptions (Part 1 of 2)