Chapter 8 S12X Debug (S12XDBGV3) Module
MC9S12XE-Family Reference Manual , Rev. 1.21
304
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8.1.2
Overview
The comparators monitor the bus activity of the CPU12X and XGATE. When a match occurs the control
logic can trigger the state sequencer to a new state. On a transition to the Final State, bus tracing is triggered
and/or a breakpoint can be generated.
Independent of comparator matches a transition to Final State with associated tracing and breakpoint can
be triggered by the external TAGHI and TAGLO signals, or by an XGATE module S/W breakpoint request
or by writing to the TRIG control bit.
The trace buffer is visible through a 2-byte window in the register address map and can be read out using
standard 16-bit word reads. Tracing is disabled when the MCU system is secured.
8.1.3
Features
Four comparators (A, B, C, and D)
— Comparators A and C compare the full address bus and full 16-bit data bus
— Comparators A and C feature a data bus mask register
— Comparators B and D compare the full address bus only
— Each comparator can be congured to monitor CPU12X or XGATE buses
— Each comparator features selection of read or write access cycles
— Comparators B and D allow selection of byte or word access cycles
— Comparisons can be used as triggers for the state sequencer
Three comparator modes
— Simple address/data comparator match mode
— Inside address range mode, Addmin
≤ Address ≤ Addmax
— Outside address range match mode, Address
< Addmin or Address > Addmax
Two types of triggers
— Tagged — This triggers just before a specic instruction begins execution
— Force — This triggers on the rst instruction boundary after a match occurs.
The following types of breakpoints
— CPU12X breakpoint entering BDM on breakpoint (BDM)
— CPU12X breakpoint executing SWI on breakpoint (SWI)
— XGATE breakpoint
WORD
16 bit data entity
Data Line
64 bit data entity
CPU
CPU12X module
Tag
Tags can be attached to XGATE or CPU opcodes as they enter the instruction pipe. If the tagged opcode
reaches the execution stage a tag hit occurs.
Table 8-2. Glossary Of Terms (continued)
Term
Denition