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Chapter 20 Debug (S12XDBGV2)
MC9S12XDP512 Data Sheet, Rev. 2.11
Freescale Semiconductor 817
20.4.3.4 Trigger On XGATE S/W Breakpoint Request
The XGATE S/W breakpoint request issues a forced breakpoint request to the CPU immediately
independent of DBG settings. If the debug module is armed triggers the state sequencer into the disarmed
state. Active tracing sessions are terminated immediately, thus if tracing has not yet begun using begin-
trigger, no trace information is stored. XGATE generated breakpoints are independent of the DBGBRK
bits. The XGSBPE bit in DBGC1 determines if the XGATE S/W breakpoint function is enabled. The BDM
bit in DBGC1 determines if the XGATE requested breakpoint causes the system to enter BDM mode or
initiate a software interrupt (SWI).
20.4.3.5 Immediate Trigger
At any time independent of comparator matches or external tag signals it is possible to initiate a tracing
session and/or breakpoint by writing to the TRIG bit in DBGC1. This triggers the state sequencer into the
final state and issues a forced breakpoint request to both CPU and XGATE.
20.4.3.6 Trigger Priorities
In case of simultaneous triggers, the priority is resolved according to Table 20-38. The lower priority
trigger is suppressed. It is thus possible to miss a lower priority trigger if it occurs simultaneously with a
trigger of a higher priority. The trigger priorities described in Table 20-38 dictate that in the case of
simultaneous matches, the match on the lower channel number ([0,1,2,3) has priority. The SC[3:0]
encoding ensures that a match leading to final state has priority over all other matches independent of
current state sequencer state. When configured for range modes a simultaneous match of comparators A
and C generates an active match0 while match2 is suppressed.
Table 20-38. Trigger Priorities
Priority Source Action
Highest XGATE Immediate forced breakpoint......(Tracing terminated immediately).
TRIG Enter final state
External TAGHI/TAGLO Enter State0
Match0 (force or tag hit) Trigger to next state as defined by state control registers
Match1 (force or tag hit) Trigger to next state as defined by state control registers
Match2 (force or tag hit) Trigger to next state as defined by state control registers
Lowest Match3 (force or tag hit) Trigger to next state as defined by state control registers