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Debug Module
34-55
Freescale Semiconductor
2. Signal the target address to be displayed sequentially on the PSTDDATA pins. Encodings 0x9–0xB
identify the number of bytes displayed
.
Using the PSTB, o
3. The new target address is optionally available on subsequent cycles using the PSTDDATA port.
The number of bytes of displayed on this port is configurable (2, 3, or 4 bytes, where the
PSTDDATA encoding is 0x9, 0xA, and 0xB, respectively).
Another example of a variant branch instruction would be a JMP (A0) instruction.
shows the
PSTDDATA outputs that indicate a JMP (A0) execution, assuming the CSR was programmed to display
the lower 2 bytes of an address.
Figure 34-49. Example JMP Instruction Output on PSTDDATA
PSTDDATA is driven two nibbles at a time with a 0x59; 0x5 indicates a taken branch and the marker value
0x9 indicates a 2-byte address. Therefore, the subsequent 4 nibbles display the lower two bytes of address
register A0 in least-to-most-significant nibble order. The PSTDDATA output after the JMP instruction
continues with the next instruction.
34.4.4.2
Processor Stopped or Breakpoint State Change (PST = 0xE)
The 0xE encoding is generated either as a one- or multiple-cycle issue as follows:
•
When the core is stopped by a STOP instruction, this encoding appears in multiple-cycle format.
The ColdFire processor remains stopped until an interrupt occurs; thus, PSTDDATA outputs
display 0xE until stopped mode is exited. PSTB only stores two consecutive packets of 0x1E.
•
When a breakpoint status change is to be output on PSTDDATA, 0xE is displayed for one cycle,
followed immediately with the 4-bit value of the current trigger status, where the trigger status is
left justified rather than in the CSR[BSTAT] description.
Section 34.3.2, “Configuration/Status
,” shows that status is right justified. That is, the displayed trigger status on
PSTDDATA after a single 0xE is as follows:
— 0x0 = no breakpoints enabled
— 0x2 = waiting for level-1 breakpoint
— 0x4 = level-1 breakpoint triggered
— 0xA = waiting for level-2 breakpoint
— 0xC = level-2 breakpoint triggered
Thus, 0xE can indicate multiple events, based on the next value, as
shows.
PSTDDATA
PSTCLK
0x59
A0[3–0,7–4]
A0[11–8,15–12]
Processor Clock
Содержание MCF54455
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