S12S Debug Module (S12SDBGV2)
6.4.2.2.2
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.
6.4.3
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.
6.4.3.1
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.
6.4.3.2
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.
6.4.3.3
Immediate Trigger
Independent of comparator matches it is possible to initiate a tracing session and/or breakpoint by writing
to the TRIG bit in DBGC1. If configured for begin aligned tracing, this triggers the state sequencer into
the Final State, if configured for end alignment, setting the TRIG bit disarms the module, ending the
session and issues a forced breakpoint request to the CPU.
It is possible to set both TRIG and ARM simultaneously to generate an immediate trigger, independent of
the current state of ARM.
6.4.3.4
Channel Priorities
In case of simultaneous matches the priority is resolved according to Table 6-36. The lower priority is
suppressed. It is thus possible to miss a lower priority match if it occurs simultaneously with a higher
priority. The priorities described in Table 6-36 dictate that in the case of simultaneous matches, the match
pointing to final state has highest priority followed by the lower channel number (0,1,2).
S12P-Family Reference Manual, Rev. 1.13
Freescale Semiconductor
179
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