Datasheet

217
SAM3X / SAM3A [DATASHEET]
Atmel-11057C-ATARM-SAM3X-SAM3A-Datasheet_23-Mar-15
11.5 Functional Description
11.5.1 Test Pin
One dedicated pin, TST, is used to define the device operating mode. When this pin is at low level during power-
up, the device is in normal operating mode. When at high level, the device is in test mode or FFPI mode. The TST
pin integrates a permanent pull-down resistor of about 15 kΩ,so that it can be left unconnected for normal
operation. Note that when setting the TST pin to low or high level at power up, it must remain in the same state
during the duration of the whole operation.
11.5.2 Debug Architecture
Figure 11-4 shows the SAM3 debug architecture. The Cortex-M3 embeds five functional units for debug:
 SWJ-DP (Serial Wire/JTAG Debug Port)
 FPB (Flash Patch Breakpoint)
 DWT (Data Watchpoint and Trace)
 ITM (Instrumentation Trace Macrocell)
 TPIU (Trace Port Interface Unit)
The debug architecture information that follows is mainly dedicated to developers of SWJ-DP Emulators/Probes
and debugging tool vendors for Cortex M3-based microcontrollers. For further details on SWJ-DP see the Cortex
M3 technical reference manual.
Figure 11-4. Debug Architecture
11.5.3 Serial Wire/JTAG Debug Port (SWJ-DP)
The Cortex-M3 embeds a SWJ-DP Debug port which is the standard CoreSight
™
debug port. It combines Serial
Wire Debug Port (SW-DP), from 2 to 3 pins and JTAG debug Port (JTAG-DP), 5 pins.
By default, the JTAG Debug Port is active. If the host debugger wants to switch to the Serial Wire Debug Port, it
must provide a dedicated JTAG sequence on TMS/SWDIO and TCK/SWCLK which disables JTAG-DP and
enables SW-DP.
When the Serial Wire Debug Port is active, TDO/TRACESWO can be used for trace. The asynchronous TRACE
output (TRACESWO) is multiplexed with TDO. So the asynchronous trace can only be used with SW-DP, not
JTAG-DP.
4 watchpoints
PC sampler
data address sampler
data sampler
interrupt trace
CPU statistics
DWT
6 breakpoints
FPB
software trace
32 channels
time stamping
ITM
SWD/JTAG
SWJ-DP
SWO trace
TPIU