IDT EJTAG System
Hardware Breakpoints
79RC32438 User Reference Manual
20 - 37
November 4, 2002
Notes
Conditions for Matching Data Breakpoints
When a data breakpoint is enabled, that breakpoint is evaluated in Non-Debug Mode with both the
access address of every data access due to load/store instructions (including loads/stores of coprocessor
registers) and the address causing address errors upon data access. Data breakpoints are not evaluated
with addresses from PREF (prefetch) or CACHE instructions.
The concept “data bus” is used in the following to denote the bytes accessed and the data value trans-
ferred in a load/store operation. In this notation data bus referees to the naturally-aligned memory word (for
32-bit processors) or doubleword (for 64-bit processors) containing the accessed address referred to as
ADDR. This notation is independent of the actual width of the processor bus, e.g., the “data bus” width of a
64-bit processor is 64, even if that processor has a 32-bit processor bus. A match of the data breakpoint
depends on a number of parameters, shown in Table 20.23. The fields in the data breakpoint registers are
in the form REG
FIELD
.
Reference
Description
Width
TYPE
Data access type is either load or store.
No width
DBCn
NoSB
Controls whether condition for data breakpoint is ful-
filled on a store access:
0: Condition can be fulfilled on store access
1: Condition is never fulfilled on store access
1 bit
DBCn
NoLB
Controls whether condition for data breakpoint is ful-
filled on a load access:
0:
Condition can be fulfilled on load access
1:
Condition is never fulfilled on load access
1 bit
ASID
ASID field in EntryHi CP0 register.
8 bits
DBCn
ASIDuse
ASID value used in compare for data breakpoint n:
0: Do not use ASID value in compare
1: Use ASID value in compare
1 bit
DBASIDn
ASID
Conditional Data breakpoint n ASID value for com-
parison.
8 bits
ADDR
Virtual address of data access, effective address.
32 / 64 bits
DBAn
DBA
Data breakpoint n address for compare with condi-
tions.
32 / 64 bits
DBMn
DBM
Conditional Data breakpoint n address mask:
0: Corresponding address bit compared
1: Corresponding address bit masked
32 / 64 bits
BYTELANE
Byte lane access indication, where BYTELANE[0] is
1 only if the byte at bits [7:0] of the data bus is
accessed, BYTELANE[1] is 1 only if the byte at bits
[15:8] of the data bus is accessed, etc.
4 / 8 bits
DBCn
BAI
Determines whether access is ignored to specific
bytes. BAI[0] controls ignore of access to the byte at
bits [7:0] of the data bus, BAI[1] ignores access to
byte at bits [15:8] of the data bus, etc.:
0: Condition depends on access to corresponding
byte
1: Access for corresponding byte is ignored
4 / 8 bits
Table 20.23 Data Breakpoint Condition Parameters (Part 1 of 2)