S9S12G48F1CLC Datasheet, PDF (344/1292 Pages) Freescale Semiconductor, Inc – Microcontrollers

S12S Debug Module (S12SDBGV2)
8.4.6 Tagging
A tag follows program information as it advances through the instruction queue. When a tagged instruction
reaches the head of the queue a tag hit occurs and can initiate a state sequencer transition.
Each comparator control register features a TAG bit, which controls whether the comparator match causes
a state sequencer transition immediately or tags the opcode at the matched address. If a comparator is
enabled for tagged comparisons, the address stored in the comparator match address registers must be an
opcode address.
Using Begin trigger together with tagging, if the tagged instruction is about to be executed then the
transition to the next state sequencer state occurs. If the transition is to the Final State, tracing is started.
Only upon completion of the tracing session can a breakpoint be generated. Using End alignment, when
the tagged instruction is about to be executed and the next transition is to Final State then a breakpoint is
generated immediately, before the tagged instruction is carried out.
R/W monitoring, access size (SZ) monitoring and data bus monitoring are not useful if tagging is selected,
since the tag is attached to the opcode at the matched address and is not dependent on the data bus nor on
the type of access. Thus these bits are ignored if tagging is selected.
When configured for range comparisons and tagging, the ranges are accurate only to word boundaries.
Tagging is disabled when the BDM becomes active.
8.4.7 Breakpoints
It is possible to generate breakpoints from channel transitions to final state or using software to write to
the TRIG bit in the DBGC1 register.
8.4.7.1 Breakpoints From Comparator Channels
Breakpoints can be generated when the state sequencer transitions to the Final State. If configured for
tagging, then the breakpoint is generated when the tagged opcode reaches the execution stage of the
instruction queue.
If a tracing session is selected by the TSOURCE bit, breakpoints are requested when the tracing session
has completed, thus if Begin aligned triggering is selected, the breakpoint is requested only on completion
of the subsequent trace (see Table 8-42). If no tracing session is selected, breakpoints are requested
immediately.
If the BRK bit is set, then the associated breakpoint is generated immediately independent of tracing
trigger alignment.
Table 8-42. Breakpoint Setup For CPU Breakpoints
BRK
0
0
0
TALIGN
0
0
1
DBGBRK
0
1
0
Breakpoint Alignment
Fill Trace Buffer until trigger then disarm (no breakpoints)
Fill Trace Buffer until trigger, then breakpoint request occurs
Start Trace Buffer at trigger (no breakpoints)
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