![](http://datasheet.mmic.net.cn/230000/79RC32438-200BB_datasheet_15568909/79RC32438-200BB_501.png)
IDT EJTAG System
Hardware Breakpoints
79RC32438 User Reference Manual
20 - 35
November 4, 2002
Notes
Conditions for Matching Breakpoints
A number of conditions must be fulfilled in order for a breakpoint to match on an executed instruction or
a data access. These conditions are described in the following subsections. A breakpoint only matches for
instructions executed in Non-Debug Mode, never due to instructions executed in Debug Mode.
The match of an enabled breakpoint generates a debug exception as described in section “Debug
Exceptions from Breakpoints” on page 20-40 and/or a trigger indication as described in section “Break-
points Used as Triggerpoints” on page 20-42. The BE and/or TE bits in the IBCn or DBCn registers enable
the breakpoints for breaks and triggers, respectively.
It is implementation dependent whether or not a breakpoint stalls the processor in order to evaluate the
match expression; for example, if required for timing reasons or in order to wait on a scheduled load to
return for evaluation of a data breakpoint with a data value compare. In some cases, stalling is avoided with
imprecise data breakpoints, as described in section “Debug Exception by Data Breakpoint” on page 20-40.
Conditions for Matching Instruction Breakpoints
When an instruction breakpoint is enabled, that breakpoint is evaluated in Non-Debug Mode with the
instruction boundary address (the lowest address of a byte in the instruction) of every executed instruction.
The instruction breakpoint is also evaluated on addresses usually causing an Address Error exception, a
TLB exception, or other exceptions. It is thereby possible to cause a Debug Instruction Break exception on
the destination address of a jump, even if a jump to that address would cause an Address Error exception.
The breakpoint is not evaluated on instructions from speculative fetches or execution.
A match of an instruction breakpoint depends on a number of parameters, shown in Table 20.22. The
fields in the instruction breakpoint registers are in the form REG
FIELD
.
DBMn
Data Breakpoint Address Mask n
See section “Data Break-
point Address Mask n
(DBMn) Register” on page
20-49.
DBASIDn
Data Breakpoint ASID n
See section “Data Break-
point ASID n (DBASIDn)
Register” on page 20-49.
Required with
data breakpoint n,
optional other-
wise. Not imple-
mented if
ASIDsup bit in
DBS is 0 (zero).
DBCn
Data Breakpoint Control n
See section “Data Break-
point Control n (DBCn)
Register” on page 20-49.
Required with
data breakpoint n,
optional other-
wise.
DBVn
Data Breakpoint Value n
See section “Data Break-
point Value n (DBVn) Reg-
ister” on page 20-51.
Required with
data breakpoint n,
optional other-
wise. Only imple-
mented with value
compares, shown
in DBS.
Register
Mnemonic
Register Name and
Description
Reference
Compliance
Table 20.21 Data Breakpoint Register Description (Part 2 of 2)