CET360 S12 DEMO PROGRAM #1 (C)

Transcription

1 CET360 S12 DEMO PROGRAM #1 (C) / ONE.C HCS12 Demo Program for CET Feb-2009 jss This program is the C implementation of ONE.ASM, the demo program that sets up port T as all outputs & increments it like an 8-bit up counter. The following code demonstrates a number of high-level language embedded system programming techniques including 1) access of physical I/O locations using "pointer macros" 2) use of above pointer macros in C expressions & statements 3) use of "inline" assembly code Additionally, the linker parameter file "ONE.PRM" also demonstrates 4) assignment of object components (data, code, etc) to appropriate physical memory locations 5) initialization of processor reset/interrupt vectors To "try out" this demo, perform the following simple procedure 1) enter CodeWarrior CW12 & create a new project on your disk 2) copy this file (ONE.C) to your project folder (Sources subfolder) then add it to your project 3) make sure ONE.C is active instead of main.c 4) build the project using Project->Make (or F7) 5) you should now be ready Flash your code to the S12 and run it To see the effect of the compiler & fully understand its function, examine ONE.LST after compiling this program. To have the compiler generate this file, you must turn on the "Generate Listing File" option in the compiler. This is found under the Compiler/Options settings (Alt-F7), on the Output tab. To see the effect of the linker, examine ONE.MAP after linking. To have the linker generate this file, you must turn on the "Generate a map file" option. This is found under the Linker/Options settings, Output tab. / typedef unsigned char Byte; typedef unsigned int Word; // define some MCU I/O registers as "pointer macros" #define PORTA ((volatile Byte )(0x00)) // I/O port A #define DDRA (( Byte )(0x02)) // DDR A #define PEAR (( Byte )(0x0A)) // Port E Assignment Reg #define mpear_neclk 0x10 // No External E Clock bit (when 1) #define PTT ((volatile Byte )(0x240)) // I/O Port T #define DDRT (( Byte )(0x242)) // Data Direction Reg T Byte lp_ctr; // 1-byte variable used as loop counter // function "main" is the primary routine of any C program void main() { PEAR &= ~mpear_neclk; // output ECLK on PE4 PTT = 0; // set initial port T outputs all low DDRT = 0xFF; // make port T all outputs Top / Now we switch to "inline assembly" mode, because 1) this is a timing sensitive (using CPU cycles) sequence, and 2) it would've been very hard to replicate this exact sequence in C Also the BRNs have been replaced with NOPs since CodeWarrior's code optimizer tosses them away! A NOP is 1 cycle just like BRN. / asm { loop1 movb #100,lp_ctr // initialize delay loop ctr. loop2 nop // waste some cycles... nop dec lp_ctr // decrement loop ctr bne loop2 // repeat until zero }; PTT += 1; // bump port T's output by one goto Top; // 'real' embedded programs never end! / it would've been better to use a while(1) loop instead of a goto, but this is "purer" translation of one.asm / }

2 / ONE.PRM Linker Parameter File for ONE.C demo program / / NAMES section is filled-in by compiler automatically / NAMES END / SEGMENT entries define meaningful names to address ranges / SEGMENTS RAM = READ_WRITE 0x0800 TO 0x0FFF; / unbanked FLASH ROM / ROM_4000 = READ_ONLY 0x4000 TO 0x7FFF; ROM_C000 = READ_ONLY 0xC000 TO 0xFEFF; END / PLACEMENT entries define where objects get allocated in the memory map / PLACEMENT _PRESTART, / Used in HIWARE format jump to _Startup at code start / STARTUP, / startup data structures / ROM_VAR, / constant variables / STRINGS, / string literals / VIRTUAL_TABLE_SEGMENT, / C++ virtual table segment / DEFAULT_ROM, NON_BANKED, / runtime routines which must not be banked / OTHER_ROM, COPY / copy down information how to initialize variables / INTO ROM_C000; DEFAULT_RAM INTO RAM; END / define required size of stack / STACKSIZE 0x100 / define reset vector (minimally) and other interrupt vectors / //VECTOR 0 _Startup / reset vector this is the default entry point for a C/C++ application. / // but I prefer VECTOR ADDRESS 0xFFFE _Startup

3 ONE.PRE C Compiler Preprocessor Output Listing / FILE 'C\Metrowerks Projects\HC12\one-c\Sources\one-a.c' / / 1 / / 33 / / 34 / / 35 / typedef unsigned char Byte ; / 36 / typedef unsigned int Word ; / 37 / / 38 / / 39 / / 40 / / 41 / / 42 / / 43 / / 44 / / 45 / / 46 / / 47 / Byte lp_ctr ; / 48 / / 49 / / 50 / void main ( ) / 51 / { / 52 / ( ( Byte ) ( 0x0A ) ) &= ~ 0x10 ; / 53 / ( ( volatile Byte ) ( 0x240 ) ) = 0 ; / 54 / ( ( Byte ) ( 0x242 ) ) = 0xFF ; / 55 / Top / 56 / / 57 / / 58 / / 59 / / 60 / / 61 / / 62 / / 63 / / 64 / asm { / 65 / loop1 movb # 100, lp_ctr / 66 / loop2 nop / 67 / nop / 68 / dec lp_ctr / 69 / bne loop2 / 70 / } ; / 71 / ( ( volatile Byte ) ( 0x240 ) ) += 1 ; / 72 / goto Top ; / 73 / / 74 / / 75 / } / 76 / / 77 / / 78 /

4 ONE.LST C Compiler Output Listing ANSI-C/cC++ Compiler for HC12 V Build 4047, Feb / 2 ONE.C HCS12 Demo Program for CET Feb-2006 jss 4 33 / typedef unsigned char Byte; 36 typedef unsigned int Word; // define some MCU I/O registers as "pointer macros" #define PORTA ((volatile Byte )(0x00)) // I/O port A 41 #define DDRA (( Byte )(0x02)) // DDR A 42 #define PEAR (( Byte )(0x0A)) // Port E Assignment Reg 43 #define mpear_neclk 0x10 // No External E Clock bit(when 1) 44 #define PTT ((volatile Byte )(0x240)) // I/O Port T 45 #define DDRT (( Byte )(0x242)) // Data Direction Reg T Byte lp_ctr; // 1-byte variable used as loop counter // function "main" is the primary routine of any C program 50 void main() 51 { Function main Source C\Metrowerks Projects\HC12\one-c\Sources\one-a.c 52 PEAR &= ~mpear_neclk; // output ECLK on PE d0a10 BCLR 10,#16 53 PTT = 0; // set initial port T outputs all low CLR DDRT = 0xFF; // make port T all outputs 0006 c6ff LDAB # b0242 STAB Top 56 / 57 Now we switch to "inline assembly" mode, because 58 1) this is a timing sensitive (using CPU cycles) sequence, and 59 2) it would've been very hard to replicate this exact sequence in C Also the BRNs have been replaced with NOPs since CodeWarrior's 62 code optimizer tosses them away! A NOP is 1 cycle just like BRN. 63 / 64 asm { 65 loop1 movb #100,lp_ctr // initialize delay loop ctr. 000b 180b MOVB #100,lp_ctr 66 loop2 nop // waste some cycles a7 NOP 67 nop 0011 a7 NOP 68 dec lp_ctr // decrement loop ctr DEC lp_ctr 69 bne loop2 // repeat until zero f9 BNE -5 ;abs = }; 71 PTT += 1; // bump port T's output by one INC goto Top; // 'real' embedded programs never end! 001a 20ef BRA -15 ;abs = 000b 73 / it would've been better to use a while(1) loop instead of a goto, 74 but this is "purer" translation of one.asm / 75 } 76

5 ONE.MAP Linker Map File Output PROGRAM "C\Metrowerks Projects\HC12\one-c\bin\Simulator.abs" TARGET SECTION Processor Motorola HC12 Memory Model SMALL File Format ELF\Dwarf 2.0 Linker SmartLinker V Build 4047, Feb FILE SECTION one-a.c.o Model SMALL, Lang ANSI-C Start12.c.o Model SMALL, Lang ANSI-C STARTUP SECTION Entry point 0xC029 (_Startup) _startupdata is allocated at 0xC039 and uses 23 Bytes extern struct _tagstartup { unsigned flags 0 _PFunc main 0xC056 (main) long stackoffset 0x900 unsigned nofzeroout 1 _Range pzeroout 0x800 1 _Copy tocopydownbeg 0xC072 int noflibinits 0 _LibInit libinits 0xC054 int nofinitbodies 0 _Cpp initbodies 0xC056 int noffinibodies 0 _Cpp finibodies 0xC056 } _startupdata; SECTION-ALLOCATION SECTION Section Name Size Type From To Segment.init 57 R 0xC000 0xC038 ROM_C000.startData 29 R 0xC039 0xC055 ROM_C000.text 28 R 0xC056 0xC071 ROM_C000.copy 2 R 0xC072 0xC073 ROM_C000.common 1 R/W 0x800 0x800 RAM.stack 256 R/W 0x801 0x900 RAM.vectSeg223_vect 2 R 0xFFFE 0xFFFF.vectSeg223 Summary of section sizes per section type READ_ONLY (R) 76 (dec 118) READ_WRITE (R/W) 101 (dec 257) NO_INIT (N/I) 103 (dec 259) VECTOR-ALLOCATION SECTION Address InitValue InitFunction 0xFFFE 0xC029 _Startup OBJECT-ALLOCATION SECTION Name Module Addr hsize dsize Ref Section RLIB MODULE -- one-a.c.o -- - PROCEDURES main C056 1C 28 0.text - VARIABLES lp_ctr common MODULE -- Start12.c.o -- - PROCEDURES Init C init _Startup C init - VARIABLES _startupdata C startData

6 MODULE STATISTIC Name Data Code Const one-a.c.o Start12.c.o other SECTION USE IN OBJECT-ALLOCATION SECTION SECTION ".text" main SECTION ".init" Init _Startup SECTION ".common" lp_ctr OBJECT LIST SORTED BY ADDRESS Name Addr hsize dsize Ref Section RLIB lp_ctr common Init C init _Startup C init main C056 1C 28 0.text UNUSED-OBJECTS SECTION COPYDOWN SECTION OBJECT-DEPENDENCIES SECTION Init USES _startupdata _Startup USES _startupdata Init main USES lp_ctr DEPENDENCY TREE main and _Startup Group +- main +- _Startup +- Init STATISTIC SECTION ExeFile Number of blocks to be downloaded 4 Total size of all blocks to be downloaded 118