S12S Debug Module (S12SDBGV2)
a forced match, a state sequencer transition can occur immediately on a successful match of system busses
and comparator registers. Whilst tagging, at a comparator match, the instruction opcode is tagged and only
if the instruction reaches the execution stage of the instruction queue can a state sequencer transition occur.
In the case of a transition to Final State, bus tracing is triggered and/or a breakpoint can be generated.
A state sequencer transition to final state (with associated breakpoint, if enabled) can be initiated by
writing to the TRIG bit in the DBGC1 control register.
The trace buffer is visible through a 2-byte window in the register address map and must be read out using
standard 16-bit word reads.
TAGS
TAGHITS
BREAKPOINT REQUESTS
TO CPU
SECURE
CPU BUS
TRANSITION
MATCH0
MATCH1
MATCH2
COMPARATOR A
COMPARATOR B
COMPARATOR C
TAG &
MATCH
CONTROL
LOGIC
STATE
STATE SEQUENCER
STATE
TRACE
CONTROL
TRIGGER
TRACE BUFFER
READ TRACE DATA (DBG READ DATA BUS)
Figure 6-23. DBG Overview
6.4.2
Comparator Modes
The DBG contains three comparators, A, B and C. Each comparator compares the system address bus with
the address stored in DBGXAH, DBGXAM, and DBGXAL. Furthermore, comparator A also compares
the data buses to the data stored in DBGADH, DBGADL and allows masking of individual data bus bits.
All comparators are disabled in BDM and during BDM accesses.
The comparator match control logic (see Figure 6-23) configures comparators to monitor the buses for an
exact address or an address range, whereby either an access inside or outside the specified range generates
a match condition. The comparator configuration is controlled by the control register contents and the
range control by the DBGC2 contents.
A match can initiate a transition to another state sequencer state (see 6.4.4”). The comparator control
register also allows the type of access to be included in the comparison through the use of the RWE, RW,
SZE, and SZ bits. The RWE bit controls whether read or write comparison is enabled for the associated
comparator and the RW bit selects either a read or write access for a valid match. Similarly the SZE and
S12P-Family Reference Manual, Rev. 1.13
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175
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