EFM32 Debug and Trace - AN0043 - Application Note - Energy Micro

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1 Introduction...the world's most energy friendly microcontrollersThe EFM32 microcontrollers use the ARM CoreSight TM on-chip debug and trace interface. Serial WireDebug technology (SWD), specifically the Serial Wire Debug Port (SW-DP) for the EFM32, is used asthe interface between the on-chip debug module and the development environment on a computer. SW-DP is a 2-pin debug interface which offers a high performance and low pin count alternative to JTAG.SWD is often used as an acronym for both the SW-DP and SWJ-DP (Serial Wire JTAG Debug Port).The EFM32 does not implement SWJ-DP.All EFM32 devices also include the Serial Wire Output interface which is a one wire interface for theInstrumentation Trace Macrocell (ITM) which is a CoreSight module that provides coarse-grained timestamping and software driven trace information.Some device families, including Leopard Gecko, Giant Gecko and Wonder Gecko devices also includethe CoreSight Embedded Trace Macrocell (ETM). This module provides full instruction trace over aseparate high speed trace interface. Instruction trace allows the software developer to get a morecomplete view of what goes on inside the microcontrollers CPU.2013-05-08 - an0043_Rev1.02 2 www.energymicro.com
2 EFM32 Debug and Trace System...the world's most energy friendly microcontrollersAn overview of all the different modules that makes up the CoreSight system inside the EFM32 is givenin Figure 2.1 (p. 3) . A short description of the different modules are given in the following section.Figure 2.1. Debug OverviewFPBChip boundaryDWT4 watchpointsPC sam pler*ETM triggerInterrupt trace6 breakpointsITMSoftware trace32 channelsTim e stam pingDAPLivecore accessSW-DPTPIUSWO21CPU statisticsETM*Trace port5*Instructiontrace* ETM Optional2.1 Serial Wire Debug Port (SW-DP)The SW-DP provides a low pin count bi-directional serial connection to the Debug Access Port (DAP) witha reference clock signal for synchronous operation. This is the only connection from outside the EFM32to access core registers and memory within the MCU. Through this two wire interface the debuggerhas real-time access to system/peripheral memory and debug configuration registers. Access is evenavailable without halting the processor.The communication over the SW-DP uses a three phase protocol:• A host-to-target packet request.• A target-to-host acknowledge response.• A data transfer phase, if required. This can be target-to-host or host-to-target, depending on therequest made in the first phase.More information on the CoreSight Serial Wire Debug interface and protocol can be found here:• http://infocenter.arm.com/help/topic/com.arm.doc.ddi0314h/DDI0314H_coresight_components_trm.pdf• http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0314h/Babcfacj.html2.2 Instrumentation Trace Macrocell (ITM)The ITM is a an application-driven trace source that supports printf() style debugging to trace operatingsystem and application events. The ITM is responsible for generating packets based on informationfrom multiple sources. Software can write directly to ITM stimulus registers to generate packets. TheData Watchpoint and Trace (DWT) module can also generate packets that are formatted and output by2013-05-08 - an0043_Rev1.02 3 www.energymicro.com
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EFM32 Debug and Trace - AN0043 - Application Note - Energy Micro

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