ICD 4 Glossary


Absolute Section
A GCC compiler section with a fixed (absolute) address that cannot be changed by the linker.
Absolute Variable/Function
A variable or function placed at an absolute address using the OCG compiler’s @ address syntax.
Access Memory
PIC18 Only – Special registers on PIC18 devices that allow access regardless of the setting of the Bank Select Register (BSR).
Access Entry Points
Access entry points provide a way to transfer control across segments to a function that may not be defined at link time. They support the separate linking of boot and secure application segments.
A value that identifies a location in memory.
Alphabetic Character
Alphabetic characters are those characters that are letters of the Roman alphabet (a, b, …, z, A, B, …, Z).
Alphanumeric characters are comprised of alphabetic characters and decimal digits (0,1, …, 9).
ANDed Breakpoints
Set up an ANDed condition for breaking, i.e., breakpoint 1 AND breakpoint 2 must occur at the same time before a program halt. This can only be accomplished if a data breakpoint and a program memory breakpoint occur at the same time.
Anonymous Structure
16-bit C Compiler – An unnamed structure. PIC18 C Compiler – An unnamed structure that is a member of a C union. The members of an anonymous structure may be accessed as if they were members of the enclosing union. For example, in the following code, hi and lo are members of an anonymous structure inside the union caster.

union castaway
int intval;
struct {
char lo; //accessible as caster.lo
char hi; //accessible as caster.hi
} caster;

American National Standards Institute is an organization responsible for formulating and approving standards in the United States.
A set of software and hardware that may be controlled by a PIC® microcontroller.
An archive/library is a collection of relocatable object modules. It is created by assembling multiple source files to object files and then using the archiver/librarian to combine the object files into one archive/library file. An archive/library can be linked with object modules and other archives/libraries to create executable code.
American Standard Code for Information Interchange is a character set encoding that uses 7-binary digits to represent each character. It includes upper and lower case letters, digits, symbols, and control characters.
Assembly is a programming language that describes binary machine code in a symbolic form. An assembler is a language tool that translates assembly language source code into machine code.
Assigned Section
A GCC compiler section which has been assigned to a target memory block in the linker command file.
Multiple events that do not occur at the same time. This is generally used to refer to interrupts that may occur at any time during processor execution.
Asynchronous Stimulus
Data generated to simulate external inputs to a simulator device.
GCC Characteristics of variables or functions in a C program which are used to describe machine-specific properties.
Attribute, Section
GCC Characteristics of sections, such as “executable,” “readonly,” or “data” that can be specified as flags in the assembler section directive.


The base two numbering system that uses the digits 0-1. The rightmost digit counts ones, the next counts multiples of 2, then 22 = 4, etc.
Use bookmarks to easily locate specific lines in a file. Select 'Toggle Bookmarks' on the Editor toolbar to add/remove bookmarks. Click other icons on this toolbar to move to the next or previous bookmark.
Hardware Breakpoint: An event whose execution will cause a halt. Software Breakpoint: An address where the execution of the firmware will halt. Usually achieved by a special break instruction.
Compile and link all the source files for an application.


C is a general-purpose programming language which features economy of expression, modern control flow, and data structures, and a rich set of operators. C++ is the object-oriented version of C.
Calibration Memory
A special function register or registers used to hold values for calibration of a PIC microcontroller onboard RC oscillator or other device peripherals.
Central Processing Unit
The part of a device that is responsible for fetching the correct instruction for execution, decoding that instruction, and then executing that instruction. When necessary, it works in conjunction with the Arithmetic Logic Unit (ALU) to complete the execution of the instruction. It controls the program memory address bus, the data memory address bus, and accesses to the stack.
Clean removes all intermediary project files, such as object, HEX, and debug files, for the active project. These files are recreated from other files when a project is built.
Common Object File Format (COFF): An object file of this format contains machine code, debugging, and other information.
Command Line Interface
A means of communication between a program and its user based solely on textual input and output.
Compiled Stack
A region of memory managed by the compiler in which variables are statically allocated space. It replaces a software or hardware stack when such mechanisms cannot be efficiently implemented on the target device.
A program that translates a source file written in a high-level language into machine code.
Conditional Assembly
Assembly language code that is included or omitted based on the assembly-time value of a specified expression.
Conditional Assembly
The act of compiling a program fragment only if a certain constant expression, specified by a preprocessor directive, is true.
Configuration Bits
Special-purpose bits programmed to set PIC MCU and dsPIC DSC modes of operation. A configuration bit may or may not be preprogrammed.
Control Directives
Directives in assembly language code that cause code to be included or omitted based on the assembly-time value of a specified expression.
See Central Processing Unit.
Cross Reference File
A file that references a table of symbols and a list of files that references the symbol. If the symbol is defined, the first file listed is the location of the definition. The remaining files contain references to the symbol.


Data Directives
Data directives are those that control the assembler’s allocation of program or data memory and provide a way to refer to data items symbolically; that is, by meaningful names.
Data Memory
On Microchip MCU and DSC devices, data memory (RAM) is comprised of General Purpose Registers (GPRs) and Special Function Registers (SFRs). Some devices also have EEPROM data memory.
Data Monitor and Control Interface (DMCI)
The Data Monitor and Control Interface (DMCI) is a tool in MPLAB® X IDE. The interface provides dynamic input control of application variables in projects. Application-generated data can be viewed graphically using any of four dynamically-assignable graph windows.
Debugging Information
Compiler and assembler options that, when selected, provide varying degrees of information used to debug application code. See compiler or assembler documentation for details on selecting debug options.
Deprecated Features
Features that are still supported for legacy reasons but will eventually be phased out and no longer used.
Device Programmer
A tool used to program electrically programmable semiconductor devices such as microcontrollers.
Digital Signal Controller
A digital signal controller (DSC) is a microcontroller device with digital signal processing capability, i.e., Microchip dsPIC DSC devices.
Digital Signal Processing\Digital Signal Processor
Digital signal processing (DSP) is the computer manipulation of digital signals, commonly analog signals (sound or image), which have been converted to digital form (sampled). A digital signal processor is a microprocessor that is designed for use in digital signal processing.
Statements in source code that provide control of the language tool’s operation.
Download is the process of sending data from a host to another device, such as an emulator, programmer or target board.
Debug With Arbitrary Record Format (DWARF) is a debug information format for ELF files.


Electrically Erasable Programmable Read Only Memory (EEPROM) is a special type of PROM that can be erased electrically. Data is written or erased one byte at a time. EEPROM retains its contents even when power is turned off.
An Executable and Linking Format (ELF) object file contains machine code. Debugging and other information is specified in with DWARF. ELF/DWARF provide better debugging of optimized code than COFF.
The ordering of bytes in a multi-byte object.
MPLAB PM3 – A folder containing files on how to program a device. This folder can be transferred to an SD/MMC card.
A portion of compiler-generated code that is responsible for de-allocating stack space, restoring registers and performing any other machine-specific requirement specified in the runtime model. This code executes after any user code for a given function, immediately prior to the function return.
Erasable Programmable Read Only Memory (EPROM) is a programmable read-only memory that can be erased usually by exposure to ultraviolet radiation.
Error/Error File
An error reports a problem that makes it impossible to continue processing your program. When possible, an error identifies the source file name and line number where the problem is apparent. An error file contains error messages and diagnostics generated by a language tool.
A description of a bus cycle which may include address, data, pass count, external input, cycle type (fetch, R/W), and time stamp. Events are used to describe triggers, breakpoints, and interrupts.
Executable Code
Software that is ready to be loaded for execution.
Send data out of the MPLAB IDE/MPLAB X IDE in a standardized format.
Combinations of constants and/or symbols separated by arithmetic or logical operators.
Extended Microcontroller Mode
In extended microcontroller mode, on-chip program memory as well as external memory is available. Execution automatically switches to external if the program memory address is greater than the internal memory space of the PIC18 device.
Extended Mode (PIC18 MCUs)
In Extended mode, the compiler will utilize the extended instructions (i.e., ADDFSR,ADDULNK, CALLW, MOVSF, MOVSS, PUSHL, SUBFSR and SUBULNK) and the indexed with literal offset addressing.
External Label
A label that has external linkage.
External Linkage
A function or variable has external linkage if it can be referenced from outside the module in which it is defined.
External Symbol
A symbol for an identifier that has external linkage. This may be a reference or a definition.
External Symbol Resolution
A process performed by the linker in which external symbol definitions from all input modules are collected in an attempt to resolve all external symbol references. Any external symbol references which do not have a corresponding definition cause a linker error to be reported.
External Input Line
An external input signal logic probe line (TRIGIN) for setting an event based upon external signals.
External RAM
Off-chip Read/Write memory.


Fatal Error
An error that will halt compilation immediately. No further messages will be produced.
File Registers
On-chip data memory, including General Purpose Registers (GPRs) and Special Function Registers (SFRs).
Determine by selection what data is included/excluded in a trace display or data file.
The process of replacing object file symbolic references with absolute addresses after relocation by the linker.
A type of EEPROM where data is written or erased in blocks instead of bytes.
Forced No Operation. A forced NOP cycle is the second cycle of a two-cycle instruction. Since the PIC microcontroller architecture is pipelined, it prefetches the next instruction in the physical address space while it is executing the current instruction. However, if the current instruction changes the program counter, this prefetched instruction is explicitly ignored, causing a forced NOP cycle.
Frame Pointer
A pointer that references the location on the stack that separates the stack-based arguments from the stack-based local variables. Provides a convenient base from which to access local variables and other values for the current function.
An implementation that accepts any strictly conforming program that does not use complex types and in which the use of the features specified in the library clause (ANSI‘89 standard clause 7) is confined to the contents of the standard headers <float.h>, <iso646.h>, <limits.h>, <stdarg.h>, <stdbool.h>, <stddef.h> and <stdint.h>.


General Purpose Register (GRP) is the portion of device data memory (RAM) available for general use.


A stop of program execution. Executing Halt is the same as stopping at a breakpoint.
An area of memory used for dynamic memory allocation where blocks of memory are allocated and freed in an arbitrary order determined at runtime.
HEX Code/HEX File
HEX code is executable instructions stored in a hexadecimal format code. HEX code is contained in a HEX file.
The base 16 numbering system that uses the digits 0-9 plus the letters A-F (or a-f). The digits A-F represent hexadecimal digits with values of (decimal) 10 to 15. The rightmost digit counts ones, the next counts multiples of 16, then 162 = 256, etc.
High-Level Language
A language for writing programs that is further removed from the processor than the assembly.


In-Circuit Emulator/In-Circuit Debugger: A hardware tool that debugs and programs a target device. An emulator has more features than a debugger, such as a trace. In-Circuit Emulation/In-Circuit Debug: The act of emulating or debugging with an in-circuit emulator or debugger. -ICE/-ICD: A device (MCU or DSC) with on-board in-circuit emulation or debug circuitry. This device is always mounted on a header board and used to debug with an in-circuit emulator or debugger.
In-Circuit Serial Programming (ICSP) is a method of programming Microchip embedded devices using serial communication and a minimum number of device pins.
Integrated Development Environment, as in MPLAB® X IDE.
A function or variable name.
Institute of Electrical and Electronics Engineers.
Bring data into the MPLAB® X IDE from an outside source, such as from a HEX file.
Initialized Data
Data which is defined with an initial value. In C, int myVar=5; defines a variable which will reside in an initialized data section.
Instruction Set
The collection of machine language instructions that a particular processor understands.
A sequence of bits that tells a central processing unit to perform a particular operation and can contain data to be used in the operation.
Internal Linkage
A function or variable has internal linkage if it can not be accessed from outside the module in which it is defined.
International Organization for Standardization
An organization that sets standards in many businesses and technologies, including computing and communications. Also known as ISO.
A signal to the CPU that suspends the execution of a running application and transfers control to an Interrupt Service Routine (ISR) so that the event may be processed. Upon completion of the ISR, normal execution of the application resumes.
Interrupt Handler
A routine that processes special code when an interrupt occurs.
Interrupt Service Request (IRQ)
An event that causes the processor to temporarily suspend normal instruction execution and to start executing an interrupt handler routine. Some processors have several interrupt request events allowing different priority interrupts.
Interrupt Service Routine (ISR)
Language tools: A function that handles an interrupt. MPLAB® X IDE: User-generated code that is entered when an interrupt occurs. The location of the code in program memory will usually depend on the type of interrupt that has occurred.
Interrupt Vector
Address of an interrupt service routine or interrupt handler.


An expression that refers to an object that can be examined and/or modified. An l-value expression is used on the left-hand side of an assignment.
The time between an event and its response.
See Archive/Archiver.
A language tool that combines object files and libraries to create executable code, resolving references from one module to another.
Linker Script Files
Linker script files are the command files of a linker. They define linker options and describe available memory on the target platform.
Listing Directives
Listing directives are those directives that control the assembler listing file format. They allow the specification of titles, pagination, and other listing control.
Listing File
A listing file is an ASCII text file that shows the machine code generated for each C source statement, assembly instruction, assembler directive, or macro encountered in a source file.
Little Endian
A data ordering scheme for multibyte data whereby the least significant byte is stored at the lower addresses.
Local Label
A local label is one that is defined inside a macro with the LOCAL directive. These labels are particular to a given instance of a macro’s instantiation. In other words, the symbols and labels that are declared as local are no longer accessible after the ENDM macro is encountered.
Logic Probes
Up to 14 logic probes can be connected to some Microchip emulators. The logic probes provide external trace inputs, trigger output signal, +5 V, and a common ground.
Loop-Back Test Board
Used to test the functionality of the MPLAB REAL ICE in-circuit emulator.
Low Voltage Differential Signaling (LVDS) is a low-noise, low-power, low-amplitude method for high-speed (gigabits per second) data transmission over copper wire. With standard I/O signaling, data storage is contingent upon the actual voltage level. Voltage level can be affected by wire length (longer wires increase resistance, which lowers voltage). But with LVDS, data storage is distinguished only by positive and negative voltage values, not the voltage level. Therefore, data can travel over greater lengths of wire while maintaining a clear and consistent data stream.

Source: http://www.webopedia.com/TERM/L/LVDS.html


Machine Code
The representation of a computer program that is actually read and interpreted by the processor. A program in binary machine code consists of a sequence of machine instructions (possibly interspersed with data). The collection of all possible instructions for a particular processor is known as its “instruction set”.
Machine Language
A set of instructions for a specific central processing unit, designed to be usable by a processor without being translated.
Macro instruction is an instruction that represents a sequence of instructions in an abbreviated form.
Macro Directives
Directives that control the execution and data allocation within macro body definitions.
Export to a file the instructions to make the project. Use this file to make your project outside of MPLAB IDE/MPLAB X IDE, i.e., with a make.
Make Project
A command that rebuilds an application, recompiling only those source files that have changed since the last complete compilation.
Microcontroller Unit. An abbreviation for microcontroller. Also µC.
Memory Model
For C compilers, a representation of the memory available to the application. For the PIC18 C compiler, a description that specifies the size of pointers that point to program memory.
Text displayed to alert you to potential problems in language tool operation. A message will not stop operation.
A highly integrated chip that contains a CPU, RAM, program memory, I/O ports, and timers.
Microcontroller Mode
One of the possible program memory configurations of PIC18 microcontrollers. In Microcontroller mode, only internal execution is allowed. Thus, only the on-chip program memory is available in Microcontroller mode.
Microprocessor Mode
One of the possible program memory configurations of PIC18 microcontrollers. In Microprocessor mode, the on-chip program memory is not used. The entire program memory is mapped externally.
Text instructions that can be translated directly into machine code. Also referred to as opcodes.
The preprocessed output of a source file after preprocessor directives have been executed. Also known as a translation unit.
MPASM™ Assembler
Microchip Technology’s relocatable macro assembler for PIC microcontroller devices, KeeLoq® devices, and Microchip memory devices.
Microchip in-circuit debugger that works with MPLAB IDE/MPLAB X IDE. See ICE/ICD.
Microchip’s Integrated Development Environment (IDE). MPLAB IDE/MPLAB X IDE comes with an editor, project manager and simulator.
MPLAB Language Tool for Device
Microchip’s C compilers, assemblers, and linkers for specified devices. Select the type of language tool based on the device you will be using for your application, e.g. if you will be creating C code on a PIC18 MCU, select the MPLAB C Compiler for PIC18 MCUs.
A device programmer from Microchip. Programs PIC18 microcontrollers and dsPIC digital signal controllers. Can be used with MPLAB IDE/MPLAB X IDE or stand-alone. Replaces PRO MATE II.
MPLAB REAL ICE™ In-Circuit Emulator
Microchip’s next-generation in-circuit emulator that works with MPLAB IDE/MPLAB X IDE. See ICE/ICD.
Microchip’s simulator that works with MPLAB IDE/MPLAB X IDE in support of PIC MCU and dsPIC DSC devices.
MPLAB Starter Kit for Device
Microchip’s starter kits contain everything needed to begin exploring the specified device. View a working application and then debug and program your own changes.
MPLIB™ Object Librarian
Microchip’s librarian that can work with MPLAB IDE/MPLAB X IDE. MPLIB librarian is an object librarian for use with COFF object modules created using either MPASM assembler (mpasm or mpasmwin v2.0) or MPLAB C18 C Compiler.
MPLINK™ Object Linker
MPLINK linker is an object linker for the Microchip MPASM assembler and the Microchip C18 C compiler. MPLINK linker also may be used with the Microchip MPLIB librarian. MPLINK linker is designed to be used with MPLAB IDE/MPLAB X IDE, though it does not have to be.
Most Recently Used (MRU) refers to files and windows available to be selected from MPLAB IDE/MPLAB X IDE main pull down menus.


Native Data Size
For Native trace, the size of the variable used in a Watches window must be of the same size as the selected device’s data memory: bytes for PIC18 devices and words for 16-bit devices.
Nesting Depth
The maximum level to which macros can include other macros.
MPLAB® X IDE project component.
Non-Extended Mode (PIC18 MCUs)
In Non-Extended mode, the compiler will not utilize the extended instructions nor the indexed with literal offset addressing.
Non Real Time
Refers to the processor at a breakpoint or executing single-step instructions or MPLAB IDE/MPLAB X IDE being run in Simulator mode.
Non-Volatile Storage
A storage device whose contents are preserved when its power is off.
No Operation (NOP) is an instruction that has no effect when executed except to advance the program counter.


Object Code/Object File
Object code is the machine code generated by an assembler or compiler. An object file is a file containing machine code and possibly debug information. It may be immediately executable or it may be relocatable, requiring linking with other object files, e.g., libraries, to produce a complete executable program.
Object File Directives
Directives that are used only when creating an object file.
The base 8 number system that only uses the digits 0-7. The rightmost digit counts ones, the next digit counts multiples of 8, then 82 = 64, etc.
Off-Chip Memory
Off-chip memory refers to the memory selection option for the PIC18 device where memory may reside on the target board, or where all program memory may be supplied by the emulator. The Memory tab accessed from Options>Development Mode provides the Off-Chip Memory selection dialog box.
Operational Codes. See Mnemonics.
Symbols, like the plus sign ‘+’ and the minus sign ‘-’, that are used when forming well-defined expressions. Each operator has an assigned precedence that is used to determine the order of evaluation.
One Time Programmable. EPROM devices that are not in windowed packages. Since EPROM needs ultraviolet light to erase its memory, only windowed devices are erasable.


Pass Counter
A counter that decrements each time an event (such as the execution of an instruction at a particular address) occurs. When the pass count value reaches zero, the event is satisfied. You can assign the Pass Counter to break and trace logic, and to any sequential event in the complex trigger dialog.
Personal Computer or Program Counter.
PC Host
Any PC running a supported Windows operating system.
Persistent Data
Data that is never cleared or initialized. Its intended use is so that an application can preserve data across a device Reset.
Phantom Byte
An unimplemented byte in the dsPIC architecture that is used when treating the 24-bit instruction word as if it were a 32-bit instruction word. Phantom bytes appear in dsPIC HEX files.
PIC microcontroller (MCU) refers to all Microchip microcontroller families.
PICkit 2 and 3
Microchip’s developmental device programmers with debug capability through Debug Express. See the Readme files for each tool to see which devices are supported.
MPLAB® X IDE has both built-in components and plug-in modules to configure the system for a variety of software and hardware tools. Several plug-in tools may be found under the 'Tools' menu.
The enclosure for an in-circuit emulator or debugger. Other names are “Puck” if the enclosure is round, and “Probe”, not be confused with logic probes.
Power-on-Reset Emulation
A software randomization process that writes random values in data RAM areas to simulate uninitialized values in RAM upon initial power application.
A directive that has meaning to a specific compiler. Often a pragma is used to convey implementation-defined information to the compiler.
Rules that define the order of evaluation in expressions.
Production Programmer
A production programmer is a programming tool that has resources designed in to program devices rapidly. It has the capability to program at various voltage levels and completely adheres to the programming specification. Programming a device as fast as possible is of prime importance in a production environment where time is of the essence as the application circuit moves through the assembly line.
For MPLAB SIM simulator, a summary listing of executed stimulus by register.
Program Counter
The location that contains the address of the instruction that is currently executing.
Program Counter Unit
16-bit assembler – A conceptual representation of the layout of program memory. The program counter increments by two for each instruction word. In an executable section, two program counter units are equivalent to three bytes. In a read-only section, two program counter units are equivalent to two bytes.
Program Memory
MPLAB® X IDE: The memory area in a device where instructions are stored. Also, the memory in the emulator or simulator containing the downloaded target application firmware. 16-bit assembler/compiler: The memory area in a device where instructions are stored.
A project contains the files needed to build an application (source code, linker script files, etc.) along with their associations to various build tools and build options.
A portion of compiler-generated code that is responsible for allocating stack space, preserving registers, and performing any other machine-specific requirement specified in the runtime model. This code executes before any user code for a given function.
Prototype System
A term referring to a user's target application, or target board.
The OCG equivalent of a GCC section, short for program section. A block of code or data which is treated as a whole by the linker.
PWM Signals
Pulse Width Modulation Signals. Certain PIC MCU devices have a PWM peripheral.


An address or an address range used by the Pass Counter or as an event before another operation in a complex trigger.


The number base, HEX, or decimal, used in specifying an address.
Random Access Memory (Data Memory). Memory in which information can be accessed in any order.
Raw Data
The binary representation of code or data associated with a section.
Read Only Memory
Memory hardware that allows fast access to permanently stored data but prevents addition to or modification of the data.
Real Time
When an in-circuit emulator or debugger is released from the halt state, the processor runs in Real Time mode and behaves exactly as the normal chip would behave. In Real Time mode, the real-time trace buffer of an emulator is enabled and constantly captures all selected cycles and all break logic is enabled. In an in-circuit emulator or debugger, the processor executes in real time until a valid breakpoint causes a halt, or until the user halts the execution. In the simulator, real-time simply means the execution of the microcontroller instructions as fast as they can be simulated by the host CPU.
Recursive Calls
A function that calls itself, either directly or indirectly.
The concept that a function or macro, having been defined, can call itself. Great care should be taken when writing recursive macros; it is easy to get caught in an infinite loop where there will be no exit from the recursion.
A function that may have multiple, simultaneously active instances. This may happen due to either direct or indirect recursion or through execution during interrupt processing.
The process of converting an instruction to an identical, but smaller instruction. This is useful for saving on code size. MPLAB XC16 currently knows how to relax a CALL instruction into an RCALL instruction. This is done when the symbol that is being called is within +/- 32 k instruction words from the current instruction.
An object whose address has not been assigned to a fixed location in memory.
Relocatable Section
16-bit assembler – A section whose address is not fixed (absolute). The linker assigns addresses to relocatable sections through a process called relocation.
A process performed by the linker in which absolute addresses are assigned to relocatable sections and all symbols in the relocatable sections are updated to their new addresses.
Read Only Memory (Program Memory). Memory that cannot be modified.
The command that releases the emulator from halt, allowing it to run the application code and change or respond to I/O in real time.
Run-time Model
Describes the use of target architecture resources.
Runtime Watch
A Watches window where the variables change in as the application is run. See individual tool documentation to determine how to set up a runtime watch. Not all tools support runtime watches.


For MPLAB SIM simulator, a particular setup for stimulus control.
The GCC equivalent of an OCG psect. A block of code or data which is treated as a whole by the linker.
Section Attribute
A GCC characteristic ascribed to a section (e.g., an access section).
Sequenced Breakpoints
Breakpoints that occur in a sequence. The sequence execution of breakpoints is bottom-up; the last breakpoint in the sequence occurs first.
Serialized Quick Turn Programming
Serialization allows you to program a serial number into each microcontroller device that the Device Programmer programs. This number can be used as an entry code, password, or ID number.
The MPASM assembler shell is a prompted input interface to the macro assembler. There are two MPASM assembler shells: one for the DOS version and one for the Windows operating system version.
A software program that models the operation of devices.
Single Step
This command steps through code, one instruction at a time. After each instruction, MPLAB® X IDE updates register windows, watch variables, and status displays so you can analyze and debug instruction execution. You can also single step C compiler source code, but instead of executing single instructions, MPLAB IDE/MPLAB X IDE will execute all assembly level instructions generated by the line of the high level C statement.
The information associated with the execution of an instruction appears on the processor bus at different times. For example, the executed opcodes appears on the bus as a fetch during the execution of the previous instruction, the source data address and value and the destination data address appear when the opcode is actually executed, and the destination data value appears when the next instruction is executed. The trace buffer captures the information that is on the bus at one instance. Therefore, one trace buffer entry will contain execution information for three instructions. The number of captured cycles from one piece of information to another for a single instruction execution is referred to as the skew.
When a hardware breakpoint is used to halt the processor, one or more additional instructions may be executed before the processor halts. The number of extra instructions executed after the intended breakpoint is referred to as the skid.
Source Code
The form in which a computer program is written by the programmer. Source code is written in a formal programming language that can be translated into machine code or executed by an interpreter.
Source File
An ASCII text file containing source code.
Special Function Registers (SFRs)
The portion of data memory (RAM) dedicated to registers that control I/O processor functions, I/O status, timers, or other modes or peripherals.
See Serialized Quick Turn Programming.
Stack, Hardware
Locations in PIC microcontroller where the return address is stored when a function call is made.
Stack, Software
Memory used by an application for storing return addresses, function parameters, and local variables. This memory is dynamically allocated at runtime by instructions in the program. It allows for reentrant function calls.
Stack, Compiled
A region of memory managed and allocated by the compiler in which variables are statically assigned space. It replaces a software stack when such mechanisms cannot be efficiently implemented on the target device. It precludes reentrancy.
Static RAM or SRAM
Static Random Access Memory (SRAM) is program memory you can read/write on the target board that does not need refreshing frequently.
Status Bar
The Status Bar is located on the bottom of the MPLAB® X IDE window and indicates such current information as cursor position, development mode and device, and active toolbar.
Step Into
This command is the same as Single Step. Step Into (as opposed to Step Over) follows a CALL instruction into a subroutine.
Step Over
Step Over allows you to debug code without stepping into subroutines. When stepping over a CALL instruction, the next breakpoint will be set at the instruction after the CALL. If for some reason the subroutine gets into an endless loop or does not return properly, the next breakpoint will never be reached. The Step Over command is the same as Single Step except for its handling of CALL instructions.
Step Out
Step Out allows you to step out of a subroutine that you are currently stepping through. This command executes the rest of the code in the subroutine and then stops execution at the return address to the subroutine.
Input to the simulator, i.e., data generated to exercise the response of simulation to external signals. Often the data is put into the form of a list of actions in a text file. Stimulus may be asynchronous, synchronous (pin), clocked, and register.
A counter for measuring execution cycles.
Storage Class
Determines the lifetime of the memory associated with the identified object.
Storage Qualifier
Indicates special properties of the objects being declared (e.g., const).
A symbol is a general purpose mechanism for describing the various pieces which comprise a program. These pieces include function names, variable names, section names, file names, struct/enum/union tag names, etc. Symbols in MPLAB® X IDE refer mainly to variable names, function names and assembly labels. The value of a symbol after linking is its value in memory.
Symbol, Absolute
Represents an immediate value such as a definition through the assembly .equ directive.
System Window Control
The system window control is located in the upper left corner of windows and some dialogs. Clicking on this control usually pops up a menu that has the options 'Minimize,' 'Maximize,' and 'Close.'


Refers to user hardware.
Target Application
Software residing on the target board.
Target Board
The circuitry and programmable device that makes up the target application.
Target Processor
The microcontroller device on the target application board.
Lines of text that you build for inserting into your files at a later time. The MPLAB Editor stores templates in template files.
Tool Bar
A row or column of icons that you can click on to execute MPLAB® X IDE functions.
Tool Bar
An emulator or simulator function that logs program execution. The emulator logs program execution into its trace buffer which is uploaded to the MPLAB® X IDE trace window.
Trace Memory
Trace memory contained within the emulator. Trace memory is sometimes called the trace buffer.
Trace Macro
A macro that will provide trace information from emulator data. Since this is a software trace, the macro must be added to code, the code must be recompiled or reassembled, and the target device must be programmed with this code before trace will work.
Trigger Output
Trigger output refers to an emulator output signal that can be generated at any address or address range and is independent of the trace and breakpoint settings. Any number of trigger output points can be set.
Three-character sequences, all starting with ??, that are defined by ISO C as replacements for single characters.


Unassigned Section
A section that has not been assigned to a specific target memory block in the linker command file. The linker must find a target memory block in which to allocate an unassigned section.
Uninitialized Data
Data which is defined without an initial value. In C, int myVar; defines a variable which will reside in an uninitialized data section.
The Upload function transfers data from a tool, such as an emulator or programmer, to the host computer or from the target board to the emulator.
Universal Serial Bus (USB) is an external peripheral interface standard for communication between a computer and external peripherals over a cable using bi-serial transmission. USB 1.0/1.1 supports data transfer rates of 12 Mbps. Also referred to as high-speed USB, USB 2.0 supports data rates up to 480 Mbps.


The memory locations that an application will jump to when either a Reset or interrupt occurs.
A variable qualifier which prevents the compiler from applying optimizations that affect how the variable is accessed in memory.


MPLAB® X IDE: An alert that is provided to warn you of a situation that would cause physical damage to a device, software file, or equipment. 16-bit assembler/compiler – Warnings report conditions that may indicate a problem, but do not halt processing.
Watch Variable
A variable that you may monitor during a debugging session in a Watches window.
Watches Window
Watches windows contain a list of watch variables that are updated at each breakpoint.
Watchdog Timer (WDT)
A timer on a PIC microcontroller that resets the processor after a selectable length of time. The WDT is enabled or disabled and set up using Configuration bits.
For MPLAB SIM stimulator, a setup for generation of SCL stimulus.
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