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Debug Support
MCF5272 ColdFire
®
Integrated Microprocessor User’s Manual, Rev. 3
Freescale Semiconductor
5-5
Another example of a variant branch instruction would be a JMP (A0) instruction.
shows when
the PST and DDATA outputs that indicate when a JMP (A0) executed, assuming the CSR was programmed
to display the lower 2 bytes of an address.
Figure 5-3. Example JMP Instruction Output on PST/DDATA
PST of 0x5 indicates a taken branch and the marker value 0x9 indicates a 2-byte address. Thus, the
subsequent 4 nibbles of DDATA display the lower 2 bytes of address register A0 in
least-to-most-significant nibble order. The PST output after the JMP instruction completes depends on the
target instruction. The PST can continue with the next instruction before the address has completely
displayed on DDATA because of the DDATA FIFO. If the FIFO is full and the next instruction has captured
values to display on DDATA, the pipeline stalls (PST = 0x0) until space is available in the FIFO.
5.4
Programming Model
In addition to the existing BDM commands that provide access to the processor’s registers and the memory
subsystem, the debug module contains nine registers to support the required functionality. These registers
are also accessible from the processor’s supervisor programming model by executing the WDEBUG
instruction (write only). Thus, the breakpoint hardware in the debug module can be read or written by the
external development system using the debug serial interface
or by the operating system running on the
processor core. Software is responsible for guaranteeing that accesses to these resources are serialized and
logically consistent. Hardware provides a locking mechanism in the CSR to allow the external
development system to disable any attempted writes by the processor to the breakpoint registers (setting
CSR[IPW]). BDM commands must not be issued if the MCF5272 is using the WDEBUG instruction to
access debug module registers or the resulting behavior is undefined.
, are treated as 32-bit quantities, regardless of the number of
implemented bits.
DDATA
PSTCLK
0x0
0x0
A[3:0]
0x5
0x9
default
PST
A[7:4]
A[11:8]
A[15:12]
default
default
default
Содержание MCF5272 ColdFire
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