MC9S12GRMV1 Datasheet, PDF (337/1292 Pages) Freescale Semiconductor, Inc – MC9S12G Family Reference Manual and Data Sheet

S12S Debug Module (S12SDBGV2)
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 writing to the TRIG bit in DBGSC1, provides an immediate trigger independent of
comparator matches.
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 match on a channel
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.
8.4.4.1 Final State
On entering Final State a trigger may be issued to the trace buffer according to the trace alignment control
as defined by the TALIGN bit (see Section 8.3.2.3, “Debug Trace Control Register (DBGTCR)”). If the
TSOURCE bit in DBGTCR is clear 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.
8.4.5 Trace Buffer Operation
The trace buffer is a 64 lines deep by 20-bits wide RAM array. The DBG module stores trace information
in the RAM array in a circular buffer format. The system accesses the RAM array through a register
window (DBGTBH:DBGTBL) using 16-bit wide word accesses. After each complete 20-bit trace buffer
line is read, an internal pointer into the RAM increments so that the next read receives fresh information.
Data is stored in the format shown in Table 8-37 and Table 8-40. After each store the counter register
DBGCNT is incremented. Tracing of CPU activity is disabled when the BDM is active. Reading the trace
buffer whilst the DBG is armed returns invalid data and the trace buffer pointer is not incremented.
8.4.5.1 Trace Trigger Alignment
Using the TALIGN bit (see Section 8.3.2.3, “Debug Trace Control Register (DBGTCR)) it is possible to
align the trigger with the end or the beginning of a tracing session.
If end alignment is selected, tracing begins when the ARM bit in DBGC1 is set and State1 is entered; the
transition to Final State signals the end of the tracing session. Tracing with Begin-Trigger starts at the
opcode of the trigger. Using end alignment or when the tracing is initiated by writing to the TRIG bit whilst
configured for begin alignment, tracing starts in the second cycle after the DBGC1 write cycle.
MC9S12G Family Reference Manual, Rev.1.23
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