CodeWarrior. Microcomputer Architecture and Interfacing Colorado School of Mines Professor William Hoff

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1 CodeWarrior 1

2 Assembler An assembler is a program that translates assembly language into machine code. Machine code are the numbers that the CPU recognizes as instructions. $B6 $10 $00 Assembly language is a mnemonic (symbolic) representation of machine code, purely for human reading. LDAA $1000 Assembly program Assembler (on PC) Machine code Target Hardware (microcontroller) Assembly time or compile time Run time 2

3 CodeWarrior CodeWarrior is an integrated development environment (IDE) Free version from Freescale, Inc Get this version: Special Edition: CodeWarrior for HCS12(X) Microcontrollers (Classic). ALEDITIONS&fsrch=1&sr=1&pageNum=1. Has editor, simulator; interfaces to target hardware, debugger Assembler and C compiler We will use in class and lab Tutorial in section 3.8 in the book Approach You create a project This organizes all your files 3

4 Example Start Codewarrior On startup screen, choose Create New Project On next screen Select HCS12->HCS12C Family->MC9S12C32 Select Full Chip Simulation Hit Next On next screen Uncheck C, check Absolute assembly Enter (or browse to) the new directory location for the project Enter project name (you can leave it as Project.mcp ) Hit Finish 4

5 Template Assembly file CodeWarrior automatically creates a sample main.asm file This is a simple program to generate Fibonacci numbers You can run this program as is, or modify it It has some useful initialization stuff in there We ll first run it as is, then change it 5

6 Header comments main.asm Declarations Variables in RAM Initialization Main body of program Interrupt vectors 6

7 Assemble and Debug Select Project->Compile If there are errors you will get a popup screen Select Project->Debug This will bring up the debugger window Source code Shows assembly code with addresses CPU registers Contents of memory 7

8 Running the template program Hit Single Step to step through the program Notice the registers changing Notice count of CPU cycles Right click in the Memory window and select Address Type 800 and hit OK 8

9 Simple Fibonacci Program We ll create a simple program to generate Fibonacci numbers (Actually, the template program does this, but our program is simpler) Fibonacci numbers are a sequence defined by F n = F n-1 + F n-2 where F 0 = 0 and F 1 = 1 The sequence is 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55,... We will have three memory locations labeled N1,N2,N3 These correspond to F n-2, F n-1, F n 9

10 Simple Fibonacci Program Replace the lines Counter DS.W 1 FiboRes DS.W 1 with N1 DS.B 1 N2 DS.B 1 N3 DS.B 1 These define labels N1,N2,N3 DS.B 1 means define storage (bytes) and the number of bytes allocated is 1 Replace everything between mainloop and RTS (including those lines) with: Labels must start in column 1 loop movb movb ldaa adda staa movb movb bra #0,N1 #1,N2 N1 N2 N3 N2,N1 N3,N2 loop Initialize the first two Fibonacci numbers to be 0, 1 Add N1+N2, result in N3 Save N2 and N3 as the last two values generated Loop forever 10

11 Simple Fibonacci Program Compile and run debugger Step through program and verify that the Fibonacci numbers are produced in N3: 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55,... When does overflow occur? Number of clock cycles in the loop? Can look up the count for each instruction, in the instruction set table Or you can look at the count of CPU cycles in the simulator as you step through loop ldaa adda staa N1 N2 N3 movb N2,N1 movb N3,N2 bra loop 11

12 Other Assembler Details Comments Start with semicolon Ignored by assembler Example ldaa N ; this is a comment Syntax for numeric constants $ indicates hexadecimal (e.g., $10 has decimal value 16) % indicates binary value (e.g., % has decimal value 32) A number with no preceding symbol is decimal 12

13 Assembler Directives: org, equ These are instructions for the assembler only, not the target hardware These are used at assembly time They are not instructions that will be performed at run time org expr Tells the assembler to set the load counter to expr, the value of the operand expression Example org $1000 ldab #$FF The next item to be placed in memory (the opcode byte for ldab ) will go into $1000 label equ expr The label symbol is assigned the value of expr rather than the current load counter value Does not allocate any space Example loop_cnt equ $40 From now on, whenever the symbol loop_cnt is seen, the assembler replaces it with $40 13

14 ; Include derivative-specific definitions INCLUDE 'derivative.inc' ROMStart EQU $4000 ; absolute address to place my code/constant data ; variable/data section ORG RAMStart ; Insert here your data definition. N1 DS.B 1 N2 DS.B 1 N3 DS.B 1 ; code section ORG ROMStart Entry: _Startup: LDS #RAMEnd+1 ; initialize the stack pointer Assemble simple Fibonacci program Look at output list file (choose Project->Disassemble) CLI ; enable interrupts loop movb #0,N1 movb #1,N2 ldaa adda staa N1 N2 N3 movb N2,N1 movb N3,N2 bra loop ;************************************************************** ;* Interrupt Vectors * ;************************************************************** ORG $FFFE DC.W Entry ; Reset Vector 14

15 Memory address Contents or value Assembler list file : ROMStart EQU $4000 ; absolute address to place my code/constant data ; variable/data section ORG RAMStart ; Insert here your data definition a N1 DS.B a N2 DS.B a N3 DS.B ; code section ORG ROMStart Entry: _Startup: Notes: DS.B just defines storage space; it doesn t put anything into memory movb has a two byte opcode cli actually is implemented as andcc #$FE a CF10 00 LDS #RAMEnd+1 ; initialize the stack pointer a EF CLI ; enable interrupts a B 0008 movb #0,N a00400a 180B 0108 movb #1,N E 01 15

16 Assembler list file (continued) loop a00400f B ldaa N a BB08 01 adda N a A08 02 staa N a C 0801 movb N2,N C a00401e 180C 0802 movb N3,N Freescale HC12-Assembler (c) Copyright Freescale Notes: The value of loop is $400F The offset for BRA is $E9 or -23 decimal The value $4000 is loaded into memory at $FFFE, $FFFF Abs. Rel. Loc Obj. code Source line a E9 bra loop ;************************************************************** ;* Interrupt Vectors * ;************************************************************** ORG $FFFE a00fffe 4000 DC.W Entry ; Reset Vector 16

17 Summary The assembler translates assembly language into machine code. There are special assembler directives that are used at assembly time. Examples: org, equ, ds.b,... They tell the assembler where to load the machine code, how much storage to allocate, etc. Codewarrior An integrated development environment (IDE) Includes editor, assembler, C compiler, simulator 17

Quick Guide to Using Code Warrior

Quick Guide to Using Code Warrior So now that you have created a project, you are going to want to write an assembly program and assemble (compile) it. When you create a project a new panel appears on