
Chapter 11. Debug Support
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11-5
Real-Time Trace Support
The signal timing for the example in Table 11-2 is shown in Figure 11-3.
Figure 11-3. PSTDDATA: Single-Cycle Instruction Timing
Table 11-3 shows the case where a PSTDDATA module captures a memory operand on a
simple load instruction: mov.l <mem>,Rx.
NOTE:
A PST marker and its data display are sent contiguously.
Except for this transmission, the IDLE status (0x0) can appear
anytime. Again, given that real-time trace information appears
as a sequence of 4-bit values, there are no alignment
restrictions. That is, PST values and operands may appear on
either nibble of PSTDDATA.
11.3 Real-Time Trace Support
Real-time trace, which defines the dynamic execution path, is a fundamental debug
function. The ColdFire solution is to include a parallel output port providing encoded
processor status and data to an external development system. This 8-bit port is partitioned
Table 11-3. PSTDDATA: Data Operand Captured
Cycle
PSTDDATA[7:0]
T
{PST for mov.l, PST marker for captured operand) = {0x1, 0xB}
T+1
{0x1, 0xB}
T+2
{Operand[3:0], Operand[7:4]}
T+3
{Operand[3:0], Operand[7:4]}
T+4
{Operand[11:8], Operand[15:12]}
T+5
{Operand[11:8], Operand[15:12]}
T+6
{Operand[19:16], Operand[23:20]}
T+7
{Operand[19:16], Operand[23:20]}
T+8
{Operand[27:24], Operand[31:28]}
T+9
{Operand[27:24], Operand[31:28]}
T+10
(PST for next instruction)
T+11
(PST for next instruction,...)
PSTDDATA
PSTCLK
{A, B}
{C, D}
{E, F}
Processor Clock
T+0
T+1
T+2
T+3
T+4
T+5
T+6
F
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