MC9S12XD256MAL Datasheet, PDF (208/1348 Pages) Freescale Semiconductor, Inc – Freescale’s Scalable Controller Area Network

Chapter 6 XGATE (S12XGATEV2)
3. Tagged Breakpoints
The S12X_DBG module is able to place tags on fetched opcodes. The XGATE is able to enter
debug mode right before a tagged opcode is executed (see section 4.9 of the S12X_DBG Section).
Upon entering debug mode, the program counter will point to the tagged instruction. The other
RISC core registers will hold the result of the previous instruction.
4. Forced Breakpoints
Forced breakpoints are triggered by the S12X_DBG module (see section 4.9 of the S12X_DBG
Section). When a forced breakpoint occurs, the XGATE will enter debug mode upon completion
of the current instruction.
6.6.3 Leaving Debug Mode
Debug mode can only be left by setting the XGDBG bit to "0". If a thread is active (XGCHID has not been
cleared in debug mode), program execution will resume at the value of XGPC.
6.7 Security
In order to protect XGATE application code on secured S12X devices, a few restrictions in the debug
features have been made. These are:
• Registers XGCCR, XGPC, and XGR1–XGR7 will read zero on a secured device
• Registers XGCCR, XGPC, and XGR1–XGR7 can not be written on a secured device
• Single stepping is not possible on a secured device
6.8 Instruction Set
6.8.1 Addressing Modes
For the ease of implementation the architecture is a strict Load/Store RISC machine, which means all
operations must have one of the eight general purpose registers R0 … R7 as their source as well their
destination.
All word accesses must work with a word aligned address, that is A[0] = 0!
MC9S12XDP512 Data Sheet, Rev. 2.21
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Freescale Semiconductor