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Debug Module
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processor status and data to an external development system. This 8-bit port is partitioned into two
consecutive 4-bit nibbles. Each nibble can either transmit information concerning the processor’s
execution status (PST) or debug data (DDATA). A PST marker and its data display are sent contiguously
— the IDLE status (0x0) can appear anytime. As stated before, PST values and operands may appear on
either nibble of PSTDDATA. The processor status may not be related to the current bus transfer, due to the
decoupling FIFOs.
External development systems can use PSTDDATA outputs with an external image of the program to
completely track the dynamic execution path. This tracking is complicated by any change in flow, where
branch target address calculation is based on the contents of a program-visible register (variant
addressing). PSTDDATA outputs can display the target address of such instructions in sequential nibble
increments across multiple processor clock cycles, as described in
Section 34.4.4.1, “Begin Execution of
. Four 32-bit storage elements form a FIFO buffer connecting the processor’s
high-speed local bus to the external development system through PSTDDATA[7:0]. The buffer captures
branch target addresses and certain data values for eventual display on the PSTDDATA port, two nibbles
at a time starting with the least significant bit (lsb).
Execution speed is affected only when three storage elements contain valid data
to be dumped to the
PSTDDATA port. This occurs only when two values are captured simultaneously in a read-modify-write
operation. The core stalls until two FIFO entries are available.
shows the encoding of these signals.
Table 34-30. Processor Status Encoding
PST[3:0]
Definition
0x0
Continue execution. Many instructions execute in one processor cycle. If an instruction requires more clock
cycles, subsequent clock cycles are indicated by driving PSTDDATA outputs with this encoding.
0x1
Begin execution of one instruction. For most instructions, this encoding signals the first processor clock cycle
of an instruction’s execution. Certain change-of-flow opcodes, plus the PULSE and WDDATA instructions,
generate different encodings.
0x2
Begin execution of two instructions. For superscalar instruction dispatches, this encoding signals the first
clock cycle of the simultaneous instructions’ execution.
0x3
Entry into user-mode. Signaled after execution of the instruction that caused the ColdFire processor to enter
user mode. If the display of the ASID is enabled (CSR[OTE] = 1), the following occurs:
The 8-bit ASID follows the instruction address; that is, the PSTDDATA sequence is {0x3, 0x5, marker,
instruction address, 0x8, ASID}, where 0x8 is the ASID data marker.
When the current ASID is loaded by the privileged MOVEC instruction, the ASID is displayed on PSTDDATA.
The resulting PSTDDATA sequence for the MOVEC instruction is then {0x1, 0x8, ASID}, where the 0x8 is
the data marker for the ASID.
0x4
Begin execution of PULSE and WDDATA instructions. PULSE defines logic analyzer triggers for debug
and/or performance analysis. WDDATA lets the core write any operand (byte, word, or longword) directly to
the PSTDDATA port, independent of debug module configuration. When WDDATA is executed, a value of
0x4 is signaled, followed by the appropriate marker, and then the data transfer on the PSTDDATA port.
Transfer length depends on the WDDATA operand size.
Summary of Contents for MCF54455
Page 33: ...xxviii Freescale Semiconductor ...
Page 67: ...Freescale Semiconductor 1 ...
Page 125: ...Freescale Semiconductor 1 ...
Page 145: ...Enhanced Multiply Accumulate Unit EMAC 5 21 Freescale Semiconductor ...
Page 173: ...Cache 6 28 Freescale Semiconductor ...
Page 179: ...Static RAM SRAM 7 6 Freescale Semiconductor ...
Page 207: ...Power Management 9 16 Freescale Semiconductor ...
Page 323: ...Reset Controller Module 13 8 Freescale Semiconductor ...
Page 389: ...Pin Multiplexing and Control 16 44 Freescale Semiconductor ...
Page 575: ...PCI Bus Controller 22 58 Freescale Semiconductor ...
Page 600: ...Advanced Technology Attachment ATA Freescale Semiconductor 23 25 ...
Page 601: ...Freescale Semiconductor 1 ...
Page 842: ...I2 C Interface Freescale Semiconductor 33 16 ...
Page 843: ...Freescale Semiconductor 1 ...
Page 921: ...Revision History A 6 Freescale Semiconductor ...