S12S Debug Module (S12SDBGV2)
MC9S12G Family Reference Manual Rev.1.27
340 NXP Semiconductors
If the comparator register contents coincide with the SWI/BDM vector address then an SWI in user code
could coincide with a DBG breakpoint. The CPU ensures that BDM requests have a higher priority than
SWI requests. Returning from the BDM/SWI service routine care must be taken to avoid a repeated
breakpoint at the same address.
Should a tagged or forced breakpoint coincide with a BGND in user code, then the instruction that follows
the BGND instruction is the first instruction executed when normal program execution resumes.
NOTE
When program control returns from a tagged breakpoint using an RTI or
BDM GO command without program counter modification it returns to the
instruction whose tag generated the breakpoint. To avoid a repeated
breakpoint at the same location reconfigure the DBG module in the SWI
routine, if configured for an SWI breakpoint, or over the BDM interface by
executing a TRACE command before the GO to increment the program
flow past the tagged instruction.
8.5 Application Information
8.5.1 State Machine scenarios
Defining the state control registers as SCR1,SCR2, SCR3 and M0,M1,M2 as matches on channels 0,1,2
respectively. SCR encoding supported by S12SDBGV1 are shown in black. SCR encoding supported only
in S12SDBGV2 are shown in red. For backwards compatibility the new scenarios use a 4th bit in each SCR
register. Thus the existing encoding for SCRx[2:0] is not changed.
8.5.2 Scenario 1
A trigger is generated if a given sequence of 3 code events is executed.
Figure 8-27. Scenario 1
Scenario 1 is possible with S12SDBGV1 SCR encoding
State1
Final State
State3
State2
SCR1=0011
SCR2=0010
SCR3=0111
M1
M2
M0
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