S912XHZ512F1VAG Datasheet, PDF (793/978 Pages) Freescale Semiconductor, Inc – Covers MC9S12XHZ384, MC9S12XHZ256

Chapter 22 S12X Debug (S12XDBGV3) Module
then state1 of the state sequencer is entered. Further transitions between the states are then controlled by
the state control registers and depend upon a selected trigger mode condition being met. From Final State
the only permitted transition is back to the disarmed state0. Transition between any of the states 1 to 3 is
not restricted. Each transition updates the SSF[2:0] flags in DBGSR accordingly to indicate the current
state.
Alternatively by setting the TRIG bit in DBGSC1, the state machine can be triggered to state0 or Final
State depending on tracing alignment.
A tag hit through TAGHI/TAGLO brings the state sequencer immediately into state0, causes a breakpoint,
if breakpoints are enabled, and ends tracing immediately independent of the trigger alignment bits
TALIGN[1:0].
Independent of the state sequencer, each comparator channel can be individually configured to generate an
immediate breakpoint when a match occurs through the use of the BRK bits in the DBGxCTL registers.
Thus it is possible to generate an immediate breakpoint on selected channels, whilst a state sequencer
transition can be initiated by a match on other channels. If a debug session is ended by a trigger on a
channel with BRK = 1, the state sequencer transitions through Final State for a clock cycle to state0. This
is independent of tracing and breakpoint activity, thus with tracing and breakpoints disabled, the state
sequencer enters state0 and the debug module is disarmed.
An XGATE S/W breakpoint request, if enabled causes a transition to the State0 and generates a breakpoint
request to the CPU12X immediately
22.4.4.1 Final State
On entering Final State a trigger may be issued to the trace buffer according to the trace position control
as defined by the TALIGN field (see Section 22.3.2.3”). If TSOURCE in the trace control register
DBGTCR are cleared then the trace buffer is disabled and the transition to Final State can only generate a
breakpoint request. In this case or upon completion of a tracing session when tracing is enabled, the ARM
bit in the DBGC1 register is cleared, returning the module to the disarmed state0. If tracing is enabled, a
breakpoint request can occur at the end of the tracing session. If neither tracing nor breakpoints are enabled
then when the final state is reached it returns automatically to state0 and the debug module is disarmed.
22.4.5 Trace Buffer Operation
The trace buffer is a 64 lines deep by 64-bits wide RAM array. The S12XDBG module stores trace
information in the RAM array in a circular buffer format. The RAM array can be accessed through a
register window (DBGTBH:DBGTBL) using 16-bit wide word accesses. After each complete 64-bit trace
buffer line is read, an internal pointer into the RAM is incremented so that the next read will receive fresh
information. Data is stored in the format shown in Table 22-43. After each store the counter register bits
DBGCNT[6:0] are incremented. Tracing of CPU12X activity is disabled when the BDM is active but
tracing of XGATE activity is still possible. Reading the trace buffer whilst the DBG is armed returns
invalid data and the trace buffer pointer is not incremented.
MC9S12XHZ512 Data Sheet Rev. 1.06
Freescale Semiconductor
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