MPLAB C32 C COMPILER USER'S GUIDE

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MPLAB ® C32 C Compiler User’s Guide2.6.4 Which Multilib Directory Are Selected?This section looks at examples and provide details on which of the multilibssubdirectories are chosen.1. pic32-gcc foo.cFor this example, no command line options have been specified (i.e., the defaultcommand line options are being used). In this case, the . subdirectories areused.2. pic32-gcc -Os foo.cFor this example, the command line option for optimizing for size has beenspecified (i.e., -Os is being used). In this case, the ./size subdirectories areused.3. pic32-gcc -O2 foo.cFor this example, the command line option for optimizing has been specified,however, this command line option optimizes for neither size nor space (i.e., -O2is being used). In this case, the . subdirectories are used.4. pic32-gcc -Os -mips16 foo.cFor this example, the command line options for optimizing for size and forMIPS16 code have been specified (i.e., -Os and -mips16 are being used). Inthis case, the ./size/mips16 subdirectories are used.DS51686A-page 46© 2007 Microchip Technology Inc.
Chapter 3. InterruptsMPLAB ® C32 C COMPILERUSER’S GUIDE3.1 INTRODUCTION3.2 HIGHLIGHTSInterrupt processing is an important aspect of most microcontroller applications.Interrupts may be used to synchronize software operations with events that occur inreal time. When interrupts occur, the normal flow of software execution is suspendedand special functions are invoked to process the event. At the completion of interruptprocessing, previous context information is restored and normal execution resumes.PIC32MX devices support multiple interrupts, from both internal and external sources.The devices allow high-priority interrupts to override any lower priority interrupts thatmay be in progress.The MPLAB C32 C compiler provides full support for interrupt processing in C or inlineassembly code. This chapter presents an overview of interrupt processing.Items discussed in this chapter are:• Specifying an Interrupt Handler Function• Associating a Handler Function with an Exception Vector• Exception Handlers3.3 SPECIFYING AN INTERRUPT HANDLER FUNCTIONAn interrupt handler function handles the context save and restore to ensure that uponreturn from interrupt, the program context is maintained.3.3.1 Handler Function Context SavingThe standard calling convention for C functions will already preserve zero, s0-s7, gp,sp, and fp. k0 and k1 are used by the compiler to access and preserve non-GPRcontext, but are always accessed atomically (i.e., in sequences with global interruptsdisabled), so they need not be preserved actively. In addition to the standard registers,a handler function will actively preserve the a0-a3, t0-t9, v0, v1 and ra registers.An interrupt handler function will also actively save and restore processor statusregisters that are utilized by the handler function. Specifically, the EPC, SR, hi and loregisters are preserved as context.Handler functions specified as priority level 7 (highest priority) will use a shadowregister set to preserve the general purpose registers, enabling lower latency entry intothe application code of the handler function.3.3.2 Marking a Function as an Interrupt HandlerA function is marked as a handler function via either the interrupt attribute or theinterrupt pragma 1 . Each method is functionally equivalent to the other. The interrupt isspecified as handling interrupts of a specific priority level or for operating in singlevector mode.1. Note that pre-processor macros are not expanded in pragma directives.© 2007 Microchip Technology Inc. DS51686A-page 47
Page 1 and 2: MPLAB C32C COMPILERUSER’S GUIDE©
Page 3 and 4: Table of ContentsMPLAB ® C32 C COM
Page 5 and 6: PrefaceMPLAB ® C32 C COMPILERUSER
Page 7 and 8: PrefaceRECOMMENDED READINGThis user
Page 9 and 10: PrefaceDEVELOPMENT SYSTEMS CUSTOMER
Page 11 and 12: Chapter 1. Language SpecificsMPLAB
Page 13 and 14: Language Specifics1.5.6 limits.hThe
Page 15 and 16: Language Specifics__mips___mips_MIP
Page 17 and 18: Language SpecificsThe first_to_chec
Page 19 and 20: Language SpecificsGenerate a branch
Page 21 and 22: Language Specifics1.8.2 Options for
Page 25 and 26: Language SpecificsTABLE 1-5:-Wswitc
Page 27 and 28: Language SpecificsThe following -W
Page 29 and 30: Language SpecificsTABLE 1-6:-Wredun
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Page 39 and 40: Language SpecificsTABLE 1-11: PREPR
Page 41 and 42: Language Specifics1.8.10 Options fo
Page 43 and 44: Language SpecificsTABLE 1-15:Option
Page 45 and 46: Language Specifics1.10 COMPILING MU
Page 47 and 48: MPLAB ® C32 C COMPILERUSER’S GUI
Page 49: Library Environment2.6.2 What Multi
Page 53 and 54: Interrupts3.4.2 Vector PragmaThe ve
Page 57 and 58: Low Level Processor Control4.6 SPEC
Page 59 and 60: Low Level Processor Control4.8.1.1
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Page 65 and 66: Compiler Runtime Environment5.7 STA
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Page 69 and 70: Compiler Runtime EnvironmentFIGURE
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Page 87 and 88: Compiler Runtime Environment*/. = A
Page 89 and 90: Compiler Runtime Environment5.9 RAM
Page 93 and 94: Implementation Defined BehaviorISO
Page 95 and 96: Implementation Defined BehaviorImpl
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Implementation Defined BehaviorISO
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Implementation Defined BehaviorISO
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Implementation Defined BehaviorImpl
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MPLAB ® C32 C COMPILERUSER’S GUI
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IndexMPLAB ® C32 C COMPILERUSER’
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IndexNOTES:© 2007 Microchip Techno
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