MC9S12GRMV1 Datasheet, PDF (335/1292 Pages) Freescale Semiconductor, Inc – MC9S12G Family Reference Manual and Data Sheet

S12S Debug Module (S12SDBGV2)
range comparisons. The comparator B TAG bit is ignored in range modes. In order for a range comparison
using comparators A and B, both COMPEA and COMPEB must be set; to disable range comparisons both
must be cleared. The comparator A BRK bit is used to for the AB range, the comparator B BRK bit is
ignored in range mode.
When configured for range comparisons and tagging, the ranges are accurate only to word boundaries.
8.4.2.2.1 Inside Range (CompA_Addr ≤ address ≤ CompB_Addr)
In the Inside Range comparator mode, comparator pair A and B can be configured for range comparisons.
This configuration depends upon the control register (DBGC2). The match condition requires that a valid
match for both comparators happens on the same bus cycle. A match condition on only one comparator is
not valid. An aligned word access which straddles the range boundary is valid only if the aligned address
is inside the range.
8.4.2.2.2 Outside Range (address < CompA_Addr or address > CompB_Addr)
In the Outside Range comparator mode, comparator pair A and B can be configured for range comparisons.
A single match condition on either of the comparators is recognized as valid. An aligned word access
which straddles the range boundary is valid only if the aligned address is outside the range.
Outside range mode in combination with tagging can be used to detect if the opcode fetches are from an
unexpected range. In forced match mode the outside range match would typically be activated at any
interrupt vector fetch or register access. This can be avoided by setting the upper range limit to $3FFFF or
lower range limit to $00000 respectively.
8.4.3 Match Modes (Forced or Tagged)
Match modes are used as qualifiers for a state sequencer change of state. The Comparator control register
TAG bits select the match mode. The modes are described in the following sections.
8.4.3.1 Forced Match
When configured for forced matching, a comparator channel match can immediately initiate a transition
to the next state sequencer state whereby the corresponding flags in DBGSR are set. The state control
register for the current state determines the next state. Forced matches are typically generated 2-3 bus
cycles after the final matching address bus cycle, independent of comparator RWE/RW settings.
Furthermore since opcode fetches occur several cycles before the opcode execution a forced match of an
opcode address typically precedes a tagged match at the same address.
8.4.3.2 Tagged Match
If a CPU taghit occurs a transition to another state sequencer state is initiated and the corresponding
DBGSR flags are set. For a comparator related taghit to occur, the DBG must first attach tags to
instructions as they are fetched from memory. When the tagged instruction reaches the execution stage of
the instruction queue a taghit is generated by the CPU. This can initiate a state sequencer transition.
MC9S12G Family Reference Manual, Rev.1.23
Freescale Semiconductor
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