S9S12G64F0CLF Datasheet, PDF (338/1292 Pages) Freescale Semiconductor, Inc – Reference Manual and Data Sheet

S12S Debug Module (S12SDBGV2)
8.4.5.1.1 Storing with Begin Trigger Alignment
Storing with begin alignment, data is not stored in the Trace Buffer until the Final State is entered. Once
the trigger condition is met the DBG module remains armed until 64 lines are stored in the Trace Buffer.
If the trigger is at the address of the change-of-flow instruction the change of flow associated with the
trigger is stored in the Trace Buffer. Using begin alignment together with tagging, if the tagged instruction
is about to be executed then the trace is started. Upon completion of the tracing session the breakpoint is
generated, thus the breakpoint does not occur at the tagged instruction boundary.
8.4.5.1.2 Storing with End Trigger Alignment
Storing with end alignment, data is stored in the Trace Buffer until the Final State is entered, at which point
the DBG module becomes disarmed and no more data is stored. If the trigger is at the address of a change
of flow instruction, the trigger event is not stored in the Trace Buffer. If all trace buffer lines have been
used before a trigger event occurrs then the trace continues at the first line, overwriting the oldest entries.
8.4.5.2 Trace Modes
Four trace modes are available. The mode is selected using the TRCMOD bits in the DBGTCR register.
Tracing is enabled using the TSOURCE bit in the DBGTCR register. The modes are described in the
following subsections.
8.4.5.2.1 Normal Mode
In Normal Mode, change of flow (COF) program counter (PC) addresses are stored.
COF addresses are defined as follows:
• Source address of taken conditional branches (long, short, bit-conditional, and loop primitives)
• Destination address of indexed JMP, JSR, and CALL instruction
• Destination address of RTI, RTS, and RTC instructions
• Vector address of interrupts, except for BDM vectors
LBRA, BRA, BSR, BGND as well as non-indexed JMP, JSR, and CALL instructions are not classified as
change of flow and are not stored in the trace buffer.
Stored information includes the full 18-bit address bus and information bits, which contains a
source/destination bit to indicate whether the stored address was a source address or destination address.
NOTE
When a COF instruction with destination address is executed, the
destination address is stored to the trace buffer on instruction completion,
indicating the COF has taken place. If an interrupt occurs simultaneously
then the next instruction carried out is actually from the interrupt service
routine. The instruction at the destination address of the original program
flow gets executed after the interrupt service routine.
MC9S12G Family Reference Manual, Rev.1.23
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Freescale Semiconductor