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Debug Module
34-5
Freescale Semiconductor
34.2.1
Processor Status/Debug Data (PSTDDATA[7:0])
Processor status data outputs indicate processor status and captured address and data values. They operate
at half the processor’s frequency. Given that real-time trace information appears as a sequence of 4-bit data
values, there are no alignment restrictions; that is, the processor status (PST) values and operands may
appear on either nibble of PSTDDATA[7:0]. The upper nibble (PSTDDATA[7:4]) is the more significant
and yields values first.
The CSR register controls capturing of data values to be presented on PSTDDATA. Executing the
WDDATA instruction captures data that is displayed on PSTDDATA too. These signals are updated each
processor cycle and display two values at a time for two processor clock cycles.
shows the
PSTDDATA output for the processor’s sequential execution of single-cycle instructions (A, B, C, D...).
Cycle counts are shown relative to processor frequency. These outputs indicate the current processor
pipeline status and are not related to the current bus transfer.
The signal timing for the example in
Processor Status
Clock (PSTCLK)
Half-speed version of the processor clock. Its rising edge appears in the center of the
two-processor-cycle window of valid PSTDDATA output. PSTCLK indicates when the development
system should sample PSTDDATA values.
The following figure shows PSTCLK timing with respect to PSTDDATA.
If real-time trace is not used, setting CSR[PCD] keeps PSTCLK and PSTDDATA outputs from toggling
without disabling triggers. Non-quiescent operation can be reenabled by clearing CSR[PCD],
although the external development systems must resynchronize with the PSTDDATA output.
PSTCLK starts clocking only when the first non-zero PST value (0xC, 0xD, or 0xF) occurs during
system reset exception processing.
describes PST values.
Processor
Status/Debug Data
(PSTDDATA[7:0])
These outputs, which change on the negative edge of PSTCLK, indicate processor status and
captured address and data values and are discussed more thoroughly in
Status/Debug Data (PSTDDATA[7:0])
.”
Table 34-3. PSTDDATA: Sequential Execution of Single-Cycle Instructions
Cycles
PSTDDATA[7:0]
T+0, T+1
{PST for A, PST for B}
T+2, T+3
{PST for C, PST for D}
T+4, T+5
{PST for E, PST for F}
Table 34-2. Debug Module Signals (continued)
Signal
Description
PSTCLK
PSTDDATA
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 ...