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Chapter 11. Debug Support
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11-13
Programming Model
capabilities, the breakpoint specifications must be expanded to optionally include the
address space identifier (ASID) in these user-programmable virtual address triggers.
The core includes four PC breakpoint triggers and two sets of operand address breakpoint
triggers, each with two independent address registers (to allow specification of a range)
and a data breakpoint with masking capabilities. Core breakpoint triggers are accessible
through the serial BDM interface or written through the supervisor programming model
using the WDEBUG instruction.
Two ASID-related registers (PBAC and PBASID) are added for the PC breakpoint
qualification, and two existing registers (AATR and AATR1) are expanded for the address
breakpoint qualification.
11.4.1 Revision A Shared Debug Resources
In the Revision A implementation of the debug module, certain hardware structures are
shared between BDM and breakpoint functionality as shown in Table 11-7.
Thus, loading a register to perform a specific function that shares hardware resources is
destructive to the shared function. For example, a BDM command to access memory
overwrites an address breakpoint in ABHR. A BDM write command overwrites the data
breakpoint in DBR.
Revision B added hardware registers to eliminate these shared functions. The BAAR is
used to specify bus attributes for BDM memory commands and has the same format as the
LSB of the AATR. Note that the registers containing the BDM memory address and the
BDM data are not program visible.
11.4.2 Address Attribute Trigger Registers (AATR, AATR1)
The address attribute trigger registers (AATR and AATR1, Figure 11-6), define address
attributes and a mask to be matched in the trigger. The register value is compared with
address attribute signals from the processor’s local high-speed bus, as defined by the
setting of the trigger definition register (TDR) for AATR and the extended trigger
definition register (XTDR) for AATR1.
This register is expanded to include an optional ASID specification and a control bit that
enables the use of the ASID field.
Table 11-7. Rev. A Shared BDM/Breakpoint Hardware
Register
BDM Function
Breakpoint Function
AATR
Bus attributes for all memory commands
Attributes for address breakpoint
ABHR
Address for all memory commands
Address for address breakpoint
DBR
Data for all BDM write commands
Data for data breakpoint
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