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2016-04-28 - Giant Gecko Family - d0053_Rev1.20
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• Serial Wire Clock input (SWCLK): This pin is enabled after reset and has a built-in pull down.
• Serial Wire Data Input/Output (SWDIO): This pin is enabled after reset and has a built-in pull-up.
• Serial Wire Viewer (SWV): This pin is disabled after reset.
The debug pins can be enabled and disabled through GPIO_ROUTE, see Section 32.3.4.1 (p. 762)
. Please remeberer that upon disabling, debug contact with the device is lost. Also note that, because
the debug pins have pull-down and pull-up enabled by default, leaving them enabled might increase the
current consumption with up to 200 µA if left connected to supply or ground.
6.3.2 Embedded Trace Macrocell v3.5 (ETM)
The ETM makes it possible to trace both instruction and data from the processor in real time. The
trace can be controlled through a set of triggering and filtering resources. The resources include 4
address comparators, 2 data value comparators, 2 counters, a context ID comparator and a sequencer.
Before enabling the ETM, the AUXHFRCO clock needs to be enabled by setting AUXHFRCOEN in
CMU_OSCENCMD. The trace can be exported through a set of trace pins, which include:
• Trace Clock (TCLK): Functions as a sample clock for the trace. This pin is disabled after reset.
• Trace Data 0 - Trace Data 3 (TD0-TD3): The data pins provide the compressed trace stream. These
pins are disabled after reset.
For information on how to configure the ETM, see the ARM Embedded Trace Macrocell Architecture
Specification. The Trace Clock and Trace Data pins can be enabled through the GPIO. For more
information on how to enable the ETM Trace pins, the reader is referred to Section 32.3.4.2 (p. 762) .
6.3.3 Debug and EM2/EM3
Leaving the debugger connected when issuing a WFI or WFE to enter EM2 or EM3 will make the system
enter a special EM2. This mode differs from regular EM2 and EM3 in that the high frequency clocks
are still enabled, and certain core functionality is still powered in order to maintain debug-functionality.
Because of this, the current consumption in this mode is closer to EM1 and it is therefore important to
disconnect the debugger before doing current consumption measurements.
6.4 Debug Lock and Device Erase
The debug access to the Cortex-M3 is locked by clearing the Debug Lock Word (DLW) and resetting
the device, see Section 7.3.2 (p. 32) .
When debug access is locked, the debug interface remains accessible but the connection to the Cortex-
M3 core and the whole bus-system is blocked as shown in Figure 6.2 (p. 27) . This mechanism is
controlled by the Authentication Access Port (AAP) as illustrated by Figure 6.1 (p. 26) . The AAP is
only accessible from a debugger and not from the core.
Figure 6.1. AAP - Authentication Access Port
SW- DP
AHB- AP
Cortex
SerialWire
debug
int erface
DEVICEERASE
Aut hent icat ion
Access Port
(AAP)
ERASEBUSY
DLW[3:0] = = 0x F
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