
Chapter 8 S12X Debug (S12XDBGV3) Module
MC9S12XE-Family Reference Manual , Rev. 1.14
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Freescale Semiconductor
read or a write access if tagging is not selected. The corresponding DBGDCTL bits are ignored. The SZE
and SZ control bits are ignored in range mode. The comparator A and C TAG bits are used to tag range
comparisons for the AB and CD ranges respectively. The comparator B and D TAG bits are ignored in
range modes. In order for a range comparison using comparators A and B, both COMPEA and COMPEB
mustbeset;todisablerangecomparisonsbothmustbecleared.SimilarlyforarangeCDcomparison,both
COMPEC and COMPED must be set. If a range mode is selected SRCA and SRCC select the source
(S12X or XGATE), SRCB and SRCD are ignored. The comparator A and C BRK bits are used for the AB
and CD ranges respectively, the comparator B and D BRK bits are ignored in range mode. When
configured for range comparisons and tagging, the ranges are accurate only to word boundaries.
8.4.2.4.1
Inside Range (CompAC_Addr
≤
address
≤
CompBD_Addr)
In the Inside Range comparator mode, either comparator pair A and B or comparator pair C and D can be
configured for range comparisons by 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 will cause a trigger
only if the aligned address is inside the range.
8.4.2.4.2
Outside Range (address < CompAC_Addr or address > CompBD_Addr)
In the Outside Range comparator mode, either comparator pair A and B or comparator pair C and D can
be configured for range comparisons. A single match condition on either of the comparators is recognized
asvalid.Analignedwordaccesswhichstraddlestherangeboundarywillcauseatriggeronlyifthealigned
address is outside the range.
Outside range mode in combination with tagged triggers can be used to detect if the opcode fetches are
from an unexpected range. In forced trigger modes the outside range trigger would typically be activated
atanyinterruptvectorfetchorregisteraccess.Thiscanbeavoidedbysettingtheupperorlowerrangelimit
to $7FFFFF or $000000 respectively. Interrupt vector fetches do not cause taghits
When comparing the XGATE address bus in outside range mode, the initial vector fetch as determined by
the vector contained in the XGATE XGVBR register should be taken into consideration. The XGVBR
register and hence vector address can be modified.
8.4.3
Trigger Modes
Trigger modes are used as qualifiers for a state sequencer change of state. The control logic determines the
trigger mode and provides a trigger to the state sequencer. The individual trigger modes are described in
the following sections.
8.4.3.1
Forced Trigger On Comparator Match
If a forced trigger comparator match occurs, the trigger immediately initiates 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 for each trigger. Forced triggers are generated as soon as the
matching address appears on the address bus, which in the case of opcode fetches occurs several cycles