MPLAB XC8 PIC Assembler User's Guide for Embedded …

1 MPLAB XC8 PIC Assembler User's Guide for EmbeddedEngineersNotice to CustomersAll documentation becomes dated and this manual is no exception. Microchip tools and documentation are constantlyevolving to meet customer needs, so some actual dialogs and/or tool descriptions can differ from those in thisdocument. Please refer to our web site ( ) to obtain the latest documentation are identified with a DS number. This number is located on the bottom of each page, in front of the pagenumber. The numbering convention for the DS number is DSXXXXXA, where XXXXX is the document numberand A is the revision level of the the most up-to-date information on development tools, see the MPLAB IDE online help.

2 Select the Help menu,and then Topics to open a list of available online help files. 2020 Microchip Technology Inc. user Guide50002994A-page 1 Table of to Used in This Revision Basic Example For PIC18 Used Psects for PIC18 on the Command Basic Example For Mid-range Psects for Mid-range and Baseline with Data the Source Files, Paging and Linear Memory Source Files and Shared Concatenation And the Stack Stack Stack the and Bits And Using the Microchip Change Notification 30 Product Identification Devices Code Protection 2020 Microchip Technology Inc. user Guide50002994A-page 2 Legal 32 Quality Management 32 Worldwide Sales and 2020 Microchip Technology Inc.

3 user Guide50002994A-page 31. Conventions Used in This GuideThe following conventions may appear in this documentation:Table 1-1. Documentation ConventionsDescriptionRepresentsExamples Arial font:Italic charactersReferenced booksMPLAB IDE user s GuideEmphasized the only capsA windowthe Output windowA dialogthe Settings dialogA menu selectionselect Enable ProgrammerQuotesA field name in a window or dialog Save project before build Underlined, italic text with rightangle bracketA menu pathFile>SaveBold charactersA dialog buttonClick OKA tabClick the Power tabN RnnnnA number in verilog format, whereN is the total number of digits, R isthe radix and n is a b0010, 2 hF1 Text in angle brackets < >A key on the keyboardPress <Enter>, <F1>Courier New font:Plain Courier NewSample source code#define pathsc.

4 \mcc18\hKeywords_asm, _endasm, staticCommand-line options-Opa+, -Opa-Bit values0, 1 Constants0xFF, A Italic Courier NewA variable , where file can be any validfilenameSquare brackets [ ]Optional argumentsmcc18 [options] file [options]Curly brackets and pipe character: { | }Choice of mutually exclusivearguments; an OR selectionerrorlevel {0|1} repeated textvar_name [, ]Represents code supplied by uservoid main (void){ ..} Preface 2020 Microchip Technology Inc. user Guide50002994A-page Recommended ReadingThis user s Guide describes the use and features of the MPLAB XC8 PIC Assembler . The following Microchipdocuments are available and recommended as supplemental reference XC8 PIC Assembler User's GuideThis user s Guide describes the use and features of the MPLAB XC8 PIC XC8 PIC Assembler Migration GuideThis Guide is for customers who have MPASM projects and who wish to migrate them to the MPLAB XC8 PICassembler.

5 It describes the nearest equivalent Assembler syntax and directives for MPASM XC8 C Compiler Release Notes for PIC MCUFor the latest information on changes and bug fixes to this Assembler , read the Readme file in the docs subdirectoryof the MPLAB XC8 installation Tools Release NotesFor the latest information on using other development tools, read the tool-specific Readme files in the docssubdirectory of the MPLAB X IDE installation Document Revision HistoryRevision A (May 2020) Initial release of this document. Preface 2020 Microchip Technology Inc. user Guide50002994A-page 52. IntroductionThis Guide shows and describes example assembly programs that can be built with the MPLAB XC8 PIC Assembler (PIC Assembler ) for a variety of 8-bit Microchip PIC device examples shown bring together various concepts, Assembler directives, and operators, which you can readabout in more detail in the MPLAB XC8 PIC Assembler User's Guide The programs themselves show how device orassembler features can be utilized but do not represent meaningful you are migrating programs from the Microchip MPASM Assembler to PIC Assembler , this Guide in conjunctionwith the MPLAB XC8 PIC Assembler Migration Guide will be of great assistance.

6 Introduction 2020 Microchip Technology Inc. user Guide50002994A-page 63. A Basic Example For PIC18 DevicesAs an introduction to the PIC Assembler , consider the following example of a complete assembly program for aPIC18F47K42 device, which performs the mundane task of repeatedly reading the value on PORTA and recordingthe highest value that has been read. Aspects of this program are discussed in the sections that follow and aremostly relevant to all Basic PIC18 ExamplePROCESSOR 18F47K42#include < > // configuration word 1 CONFIG FEXTOSC=XT // crystal oscillatorCONFIG RSTOSC=EXTOSC // EXTOSC operating per FEXTOSC bitsCONFIG CLKOUTEN=OFF // CLKOUT function is disabledCONFIG PR1 WAY=ON // PRLOCK bit can be cleared and set only onceCONFIG CSWEN=ON // Writing to NOSC and NDIV is allowedCONFIG FCMEN=ON // Fail-Safe Clock Monitor enabled// configuration word 2 CONFIG MCLRE=EXTMCLR // If LVP=0, MCLR pin is MCLR.

7 If LVP=1, RE3 pin function is MCLRCONFIG PWRTS=PWRT_OFF // PWRT is disabledCONFIG MVECEN=OFF // Vector table isn't used to prioritize interruptsCONFIG IVT1 WAY=ON // IVTLOCK bit can be cleared and set only onceCONFIG LPBOREN=OFF // ULPBOR disabledCONFIG BOREN=SBORDIS // Brown-out Reset enabled, SBOREN bit is ignoredCONFIG BORV=VBOR_2P45 // Brown-out Reset Voltage (VBOR) set to ZCD=OFF // ZCD disabled, enable by setting the ZCDSEN bit of ZCDCONCONFIG PPS1 WAY=ON // PPSLOCK cleared/set only once; PPS locked after clear/set cycleCONFIG STVREN=ON // Stack full/underflow will cause ResetCONFIG DEBUG=OFF // Background debugger disabledCONFIG XINST=OFF // Extended Instruction Set and Indexed Addressing Mode disabled// configuration word 3 CONFIG WDTCPS=WDTCPS_31 // Divider ratio 1:65536; software control of WDTPSCONFIG WDTE=OFF // WDT Disabled; SWDTEN is ignoredCONFIG WDTCWS=WDTCWS_7 // window open 100%; software control.

8 Keyed access not requiredCONFIG WDTCCS=SC // Software Control// configuration word 4 CONFIG BBSIZE=BBSIZE_512 // Boot Block size is 512 wordsCONFIG BBEN=OFF // Boot block disabledCONFIG SAFEN=OFF // SAF disabledCONFIG WRTAPP=OFF // Application Block not write protectedCONFIG WRTB=OFF // Configuration registers (300000-30000Bh) not write-protectedCONFIG WRTC=OFF // Boot Block (000000-0007 FFh) not write-protectedCONFIG WRTD=OFF // Data EEPROM not write-protectedCONFIG WRTSAF=OFF // SAF not Write ProtectedCONFIG LVP=ON // Low voltage programming enabled, MCLR pin, MCLRE ignored// configuration word 5 CONFIG CP=OFF // PFM and Data EEPROM code protection disabled;objects in common (Access bank) memory PSECT udata_acsmax: DS 1 ;reserve 1 byte for maxtmp: DS 1 ;1 byte for tmp.

9 This must be linked to the reset vectorPSECT resetVec,class=CODE,reloc=2resetVec: goto main/* find the highest PORTA value read, storing this into the object max */PSECT codemain: clrf max,c ;starting point movff max,ANSELA ;write 0 to select digital input for portloop: movff PORTA,tmp ;read and store the port value movf tmp,w,c ;is this value larger than max? A Basic Example For PIC18 Devices 2020 Microchip Technology Inc. user Guide50002994A-page 7 subwf max,w,c bc loop ;no - read again movff tmp,max ;yes - record this new high value goto loop ;read again END CommentsThere are several styles of comments that can be used in assembly source comments consist of a semi-colon, ;, followed by the comment text.

10 These can be placed on a line oftheir own, such as the comment:;objects in common (Access bank) memoryas shown in 3. A Basic Example For PIC18 Devices, or they can be at the end of a line containing an instruction ordirective, as shown bolded in this example: movff PORTA,tmp ;read the portC-style comments can be used in assembly source code if the assembly source file is preprocessed. To run thepreprocessor over an assembly source file, name the file using a .S extension (upper case), or use the -xassembler-with-cpp option when you C-style comments begin with a double slash sequence, //, followed by the comment text, as seen boldedin the line:CONFIG PWRTS=PWRT_OFF // PWRT is disabledMulti-line C-style comments begin with slash-star, /*, and terminate with a star-slash sequence, */.