MPLAB X Debugging Techniques

Transcription

1 TLS MPLAB X Debugging Techniques Breakpoints Author: Rob Ostapiuk, Stu Chandler Microchip Technology

2 Objectives! Describe the four fundamental types of breakpoints! Describe the differences between hardware and software breakpoints! Set and configure each breakpoint type! Describe the two complex types of breakpoints! Set and configure complex breakpoints 2014 Slide 2

3 Breakpoints Breakpoint Types Line Hardware Breakpoints Address Data Event Line Software Breakpoints Address Sequence Tuple 2014 Slide 3

4 Hardware Breakpoints

5 Hardware Breakpoints Definition Hardware Breakpoints are implemented with comparison registers built into the target microcontroller. Upon match with the item being watched, the program halts and control is transferred to the debug executive.! Limited in number! Typically 3-4 available! Number depends on target device! Dashboard shows number of available breakpoints by type Menu: Window! Dashboard 2014 Slide 5

6 Hardware Breakpoints On-Chip Resources Available Devices PIC10F / 12F / 16F PIC16F1xxx enhanced PIC18F PIC18F enhanced PIC18FxxJ dspic30f / PIC24F dspic33f / PIC24H PIC32MX Number of Hardware Breakpoints or 5 * 1 to 5 2, 4, 6, or 10 6 * There is a limitation for these devices that only 1 data capture is available Slide 6

7 Hardware Breakpoint Types Program! Program Breakpoints! Line (source level: execute)! Address (machine level: execute, read, write) 2014 Slide 7

8 Line Breakpoints Definition A Line Breakpoint is a source level breakpoint that suspends program execution on a specific line of code. The " " icon represents line breakpoints in the editor and breakpoints windows.! Example Uses:! To view the state of the program after running a specific block of code! To determine if a block of code is ever reached! To detect whether some software or hardware event has occurred! To check program logic or calculation results! To inject "what if" test values into a program 2014 Slide 8

9 SET Procedure In the editor, click on the line number in the glyph margin Line Breakpoints How to set or clear a Line Breakpoint CLEAR In the editor, click on the breakpoint icon ( ) Click on line number to toggle breakpoint 2014 Slide 9

10 Breakpoints Customization Options: Pass Count Definition A Pass Counter is a counter that is incremented each time a breakpoint is hit. The program will not halt until the pass counter reaches the value you specify. Pass counts may be applied to most breakpoint types.! Pass Count options:! Always Break (no pass count)! Break occurs Count instructions after event! Event must occur Count times 2014 Slide 10

11 Line Breakpoints How to configure a Line Breakpoint Procedure In the editor, right click on the breakpoint icon ( ). Select Breakpoint! Properties from the popup menu. Choose Pass Count Condition Always Break Always Break Break occurs Count instructions after Event Event must occur Count times Click OK 2014 Slide 11

12 Hardware Breakpoints Skid Effect Only affects hardware breakpoints on 8- and 16-bit architectures. PC points to next instruction to execute. Instructions to execute lcdputint() Breakpoint set here Breaks here 2014 Slide 12

13 Hardware Breakpoints Skid Effect: Number of Instructions by Family Device Family Number of Instructions Skid Program Memory Data Memory PIC12F / 16F / 18F PIC12F1xxx / PIC16F1xxx PIC24F / dspic PIC32MX Single stepping to reach a breakpoint will not produce a skid Slide 13

14 Address Breakpoints Definition An Address Breakpoint is a machine level breakpoint that suspends program execution when a specific program address is accessed. The " " icon represents address breakpoints in the disassembly and breakpoints windows.! Example Uses:! To view machine state when specific instruction is executed (assembly element of a line of C code)! To view data read from or written to program memory by table read/write instructions! To determine if a program memory location is ever reached (check program pointers) 2014 Slide 14

15 Address Breakpoints How to set and configure an Address Breakpoint Procedure Open the New Breakpoint window: Debug! New Breakpoint or from the keyboard: Ctrl Shift F8 Choose Address Breakpoint Type Configure breakpoint specific Settings Choose Pass Count Condition (if available) Click OK Skid applies to address breakpoints too. A ( ) will appear at the specified address in the disassembly window Slide 15

16 Data Breakpoints Definition A Data Breakpoint is a breakpoint that suspends program execution when a specific data address is accessed. The " " icon represents data breakpoints in the Breakpoints window (Window! Debugging! Breakpoints or Alt+Shift+5).! Example Uses:! To view machine state when variable is accessed! To view machine state when specific value is read or written to a variable (catch incorrect data)! To determine if a data memory location is ever used 2014 Slide 16

17 Procedure Data Breakpoints How to set and configure a Data Breakpoint Open the New Breakpoint window: Debug! New Breakpoint or from the keyboard: Ctrl Shift F8 Choose Data Breakpoint Type Configure breakpoint specific Settings Choose Pass Count Condition (if available) Click OK 2014 Slide 17

18 Event Breakpoints Definition An Event Breakpoint is a breakpoint that suspends program execution when a particular hardware event occurs. The " " icon represents event breakpoints in the Breakpoints window (Window! Debugging! Breakpoints or Alt+Shift+5).! Example Uses:! To view machine state after stack over/underflow! To view machine state after watchdog timeout! To catch resets! 2014 Slide 18

19 Event Breakpoints How to set and configure an Event Breakpoint Procedure Open the New Breakpoint window: Debug! New Breakpoint or from the keyboard: Ctrl Choose Event Breakpoint Type Shift F8 Configure breakpoint specific Settings Clock Mode Switch Reset SLEEP Instruction Stack over/underflow Wake up Watchdog timeout Click OK 2014 Slide 19

20 Exercise Line/Data/Event Breakpoints

21 Complex Breakpoints Sequences and Tuples

22 Complex Breakpoints Sequence Definition A Sequence is a collection of breakpoints where each event must occur in a specified order before the program is stopped. Only a maximum of two sequences may be defined at any one time.! Example Uses! Examine machine state after a specific set of events have happened in a specific order 2014 Slide 22

23 How to create a sequence Procedure Right click on an existing breakpoint in the Breakpoints window. Choose Complex Breakpoint! Add To New Sequence from the popup menu. Name the sequence Original breakpoint may be seen inside the newly created sequence 2014 Slide 23

24 How to add a breakpoint to a sequence Procedure Right click on an existing breakpoint in the Breakpoints window. Choose Complex Breakpoint! Move To name from the popup menu., where name is the name of an existing sequence. Original breakpoint may be seen inside the selected sequence 2014 Slide 24

25 How to reorder a sequence Procedure Right click on an existing breakpoint in the Breakpoints window. Choose Complex Breakpoint! Move Up or Move Down from the popup menu. Breakpoint event order is changed 2014 Slide 25

26 Complex Breakpoints Tuple Definition A Tuple is a collection of breakpoints where each event must occur simultaneously before the program is stopped. Tuples are sometimes referred to as "ANDed Breakpoints".! Example Uses! To isolate a specific instance of a read/write to a register when that register may be read/written from multiple program locations For example: Break when a value of 0x10 is written to register LATA from address 0x412 in program LATA = 0x Slide 26

27 How to create a tuple Procedure Right click on an existing data or address breakpoint in the Breakpoints window. Choose Complex Breakpoint! Add To New Tuple from the popup menu. Name the tuple Original breakpoint may be seen inside the newly created tuple All other Tuple operations are the same as Sequences 2014 Slide 27

28 Exercise Tuples

29 Software Breakpoints

30 Software Breakpoints Definition Software Breakpoints are implemented by replacing the instruction at the breakpoint address with a BREAK instruction which will halt the program and turn over control to the debug executive.! Disabled by default! 10,000 available! Reprograms original instruction and resumes execution when debugger resumes! Always shows original instruction in memory view 2014 Slide 30

31 Software Breakpoints Behind The Scenes Procedure Program executes a BREAK instruction Debugger determines breakpoint was caused by a BREAK instruction Debugger replaces BREAK with original instruction and single steps 0026e NOP NOP NOP DA40000 ReservedBR 0026e 8842B0 mov.w w0,var1 0026e NOP NOP NOP Debugger reprograms the BREAK instruction Original instruction is always shown in memory view 2014 Slide 31

32 Software Breakpoints Behind The Scenes Procedure Program executes a BREAK instruction Debugger determines breakpoint was caused by a BREAK instruction Debugger replaces BREAK with original instruction and single steps 0026e NOP NOP NOP DA40000 ReservedBR 0026e 8842B0 mov.w w0,var1 0026e NOP NOP NOP No skid effects with software breakpoints Debugger reprograms the BREAK instruction Original instruction is always shown in memory view 2014 Slide 32

33 Software Breakpoints Behind The Scenes Procedure Program executes a BREAK instruction Debugger determines breakpoint was caused by a BREAK instruction Debugger replaces BREAK with original instruction and single steps 0026e NOP NOP NOP mov.w #0x55,w0 0026e 8842B0 mov.w w0,var1 0026e NOP NOP NOP Instruction swap takes an extra cycle Debugger reprograms the BREAK instruction Original instruction is always shown in memory view 2014 Slide 33

34 Software Breakpoints Behind The Scenes Procedure Program executes a BREAK instruction Debugger determines breakpoint was caused by a BREAK instruction Debugger replaces BREAK with original instruction and single steps 0026e NOP NOP NOP mov.w #0x55,w0 0026e 8842B0 mov.w w0,var1 0026e NOP NOP NOP Debugger reprograms the BREAK instruction Original instruction is always shown in memory view 2014 Slide 34

35 Software Breakpoints Behind The Scenes Procedure Program executes a BREAK instruction Debugger determines breakpoint was caused by a BREAK instruction Debugger replaces BREAK with original instruction and single steps 0026e NOP NOP NOP DA40000 ReservedBR 0026e 8842B0 mov.w w0,var1 0026e NOP NOP NOP Debugger reprograms the BREAK instruction Original instruction is always shown in memory view 2014 Slide 35

36 Software Breakpoints Behind The Scenes What you will see in MPLAB X IDE when you hit a software breakpoint: REAL ICE or ICD3 output window Running Setting software breakpoints... Setting software breakpoints complete. Target Halted 2014 Slide 36

37 ! The Good News: Software Breakpoints Benefits! Effectively unlimited number available! No skid effects! When enabled, they are set and cleared just like hardware breakpoints in the IDE 2014 Slide 37

38 ! The Bad News: Software Breakpoints Tradeoffs! Oscillator and flash programming time dependent! Time to set breakpoint! Time to replace application and BREAK instructions! Affects device endurance! Must be reprogrammed after POR! Some devices reserve additional memory resources! Not available on many older 8-bit devices 2014 Slide 38

39 Software Breakpoints Supported Resources Devices PIC10F / 12F / 16F PIC16F1xxx enhanced PIC18F PIC18F enhanced PIC18FxxJ dspic30f / PIC24F dspic33f / PIC24H PIC32MX Number of Software Breakpoints 0 Unlimited Unlimited Unlimited Unlimited Unlimited Unlimited Unlimited 2014 Slide 39

40 How to enable software breakpoints Short Method Procedure Open the project dashboard: Window! Dashboard Click on the Toggle SW BP button Requires the MPLAB REAL ICE or MPLAB ICD Slide 40

41 How to enable software breakpoints Long Method (Can be used with project configurations) Procedure Open the project properties Open Project Properties (Select Properties from bottom of popup menu) Select debug tool (REAL ICE or ICD 3) from the categories on the left Select Debug Options from the Option Categories combo box on the right Check the box next to Use Software Breakpoints Requires the MPLAB REAL ICE or MPLAB ICD Slide 41

42 Combining Breakpoints Hardware and Software! Hardware and software breakpoints may be mixed freely! Software breakpoints are automatically used when you exceed available hardware breakpoints! Software breakpoints are converted into hardware breakpoints when they are! added to a sequence! added to a tuple! assigned to the stopwatch 2014 Slide 42

43 Exercise Software Breakpoints