SAM4L Datasheet, PDF (60/1185 Pages) ATMEL Corporation – ATSAM ARM-based Flash MCU

ATSAM4L4/L2
– Fix the ATB ID to 1
• Write 0x1 into the Trace Enable Register:
– Enable the Stimulus port 0
• Write 0x1 into the Trace Privilege Register:
– Stimulus port 0 only accessed in privileged mode (Clearing a bit in this register will
result in the corresponding stimulus port being accessible in user mode.)
• Write into the Stimulus port 0 register: TPIU (Trace Port Interface Unit)
The TPIU acts as a bridge between the on-chip trace data and the Instruction Trace Macro-
cell (ITM).
The TPIU formats and transmits trace data off-chip at frequencies asynchronous to the core.
Asynchronous Mode:
The TPIU is configured in asynchronous mode, trace data are output using the single TRAC-
ESWO pin. The TRACESWO signal is multiplexed with the TDO signal of the JTAG Debug Port.
As a consequence, asynchronous trace mode is only available when the Serial Wire Debug
mode is selected since TDO signal is used in JTAG debug mode.
Two encoding formats are available for the single pin output:
• Manchester encoded stream. This is the reset value.
• NRZ_based UART byte structure
5.4.3. How to Configure the TPIU
This example only concerns the asynchronous trace mode.
• Set the TRCENA bit to 1 into the Debug Exception and Monitor Register (0xE000EDFC) to
enable the use of trace and debug blocks.
• Write 0x2 into the Selected Pin Protocol Register
– Select the Serial Wire Output – NRZ
• Write 0x100 into the Formatter and Flush Control Register
• Set the suitable clock prescaler value into the Async Clock Prescaler Register to scale the
baud rate of the asynchronous output (this can be done automatically by the debugging tool).
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