![](http://datasheet.mmic.net.cn/230000/79RC32438-200BB_datasheet_15568909/79RC32438-200BB_495.png)
IDT EJTAG System
EJTAG Processor Core Extensions
79RC32438 User Reference Manual
20 - 29
November 4, 2002
Notes
Debug Exception Program Counter Register (CP0 Register 24, Select 0)
The Debug Exception Program Counter (DEPC) register is a read/write register that contains the
address at which processing resumes after the exception has been serviced. The size of this register is 32
bits for 32-bit processors and 64 bits for 64-bit processors, even with only 32-bit virtual addressing enabled.
All bits of the DEPC register are significant and writable. A DMFC0 from the DEPC register returns the full
64-bit DEPC on 64-bit processors. Hardware updates this register on debug exceptions and exceptions in
Debug Mode.
For precise debug exceptions and precise exceptions in Debug Mode, the DEPC register contains
either:
The virtual address of the instruction that was the direct cause of the exception, or
The virtual address of the immediately preceding branch or jump instruction, when the exception-
causing instruction is in a branch delay slot, and the Debug Branch Delay (BDB) bit in the Debug
register is set.
For imprecise debug exceptions and imprecise exceptions in Debug Mode, the DEPC register contains
the address at which execution is resumed when returning to Non-Debug Mode. Figure 20.4 shows the
format of the DEPC register and Table 20.17 describes the DEPC register field.
Figure 20.4 DEPC Register Forma
DDBS
3
Indicates that a Debug Data Break Store exception occurred
on a store due to a precise data hardware break. Cleared on
exception in Debug Mode.
0: No Debug Data Break Store Exception
1: Debug Data Break Store Exception
R
Undefined
DDBL
2
Indicates that a Debug Data Break Load exception occurred on
a load due to a precise data hardware break. Cleared on
exception in Debug Mode.
0: No Debug Data Break Store Exception
1: Debug Data Break Store Exception
R
Undefined
DBp
1
Indicates that a Debug Breakpoint exception occurred. Cleared
on exception in Debug Mode.
0: No Debug Breakpoint exception
1: Debug Breakpoint exception
R
Undefined
DSS
0
Indicates that a Debug Single Step exception occurred.
Cleared on exception in Debug Mode.
0: No debug single-step exception
1: Debug single-step exception
R
Undefined
31
DEPC
0
Fields
Name Bits
Description
Read/
Write
Reset
State
Table 20.16 Debug Register Field Descriptions (Part 4 of 4)