mc9s12xd256 Freescale Semiconductor, Inc, mc9s12xd256 Datasheet - Page 693

• Manufacturer Part Number: mc9s12xd256
• Description: Hcs12x Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

Chapter 19
Debug (S12XDBGV2)
19.1
Introduction
The DBG module provides an on-chip trace buffer with flexible triggering capability to allow non-intrusive
debug of application software. The DBG module is optimized for the HCS12X 16-bit architecture and
allows debugging of both CPU and XGATE module operations.
Typically the DBG module is used in conjunction with the BDM module, whereby the user configures the
DBG module for a debugging session over the BDM interface. Once configured the DBG module is armed
and the device leaves BDM mode returning control to the user program, which is then monitored by the
DBG module. Alternatively, the DBG module can be configured over a serial interface using SWI routines.
Comparators monitor the bus activity of the CPU and XGATE modules. When a match occurs, the control
logic can trigger the state sequencer to a new state or tag an opcode. A tag hit, which occurs when the
tagged opcode reaches the execution stage of the instruction queue, can also cause a state transition.
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. This is done 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.
19.1.1
Glossary of Terms
COF: Change Of Flow. Change in the program flow due to a conditional branch, indexed jump or interrupt.
BDM : Background Debug Mode
DUG: Device User Guide, describing the features of the device into which the DBG is integrated.
WORD: 16 bit data entity
Data Line : 64 bit data entity
XGATE : S12X family programmable Direct Memory Access Module
CPU : S12X_CPU 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.
MC9S12XDP512 Data Sheet, Rev. 2.17
Freescale Semiconductor
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