ELN5622 Embedded Systems Class 2 Spring, 2003

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ELN5622Embedded SystemsClass 2Spring, 2003
Kent Orthnerkorthner_at_hotmail.com
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Resources

• Course Page
• www.ksoa.ca/eln5644/index.html
• Other Resources
• www.hc11.demon.nl

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Programming Model Instruction Set Architecture
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Instruction Set Architecture

• The set of instructions that the microprocessor
  can execute.
• Defines registers that a programmer can access
• Some registers in the microprocessor are not
  directly accessible by the programmer

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Instruction Set Characteristics

• Fixed vs. variable Length Instructions
• 68HC11
• INX 0x08
• LDX C100 0xce c1 00
• Addressing modes
• R1 ? R2 C100
• R1 ? R3 M(R3 X)
• Supported Operands
• FMUL/FDIV, INC/DEC

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Multiple Implementations

• Successful architectures have several
  implementations
• varying clock speeds
• different bus widths
• different cache sizes
• etc.
• Ie 8086 Architecture has not changed greatly
  through 8088, 80286, 80386, 80486, Pentium, etc

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Pseudo-code

• Intended to illustrate algorithms.
• Simple to understand
• Assignments
• AccA ? 1234
• AccB ? M(5678)
• Functions
• Putchar (char)
• Newchar ? getchar ()

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Pseudo-code

• Loops
• While ()
• Endwhile
• Repeat
• Until ()

• Conditionals
• If () then
• Elsif () then
• Endif

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Programmers Model

• Describes the microprocessor registers that are
  accessible by the programmer
• Includes information about the register width and
  the type of data element it may contain
• Indicate how the instructions access and
  manipulate the registers
• Some registers are not visible (IR).

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Registers

• Local memory bits inside the processor.
• Instructions use the registers to accomplish
  tasks.
• Some are general purpose
• R0 through R7
• Some are function specific.
• Program Counter
• Stack Pointer
• Condition Code

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Motorola 68HC11 Programmers Model
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Motorola 68HC11 Programmers Model

• Accumulator
• 8-bit A , B (ACCA, ACCB)
• 16-bit D (ACCD)
• Two 8-bit accumulator registers. Each may be a
  source or destination operand for 8-bit
  instructions.
• Some instructions use D as a single 16-bit
  accumulator, with A as the most significant Byte.
• Examples
• ACCA ? 64
• ACCB ? ACCB M(0074)
• ACCD ? ACCD (MM1)

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Motorola 68HC11 Programmers Model

• Index Registers
• X, Y (IX, IY)
• Two 16-bit registers X Y used primarily for
  indexed addressing.
• Examples
• IX ? 0064
• ACCD ? M(IX64)M(IX65)

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Motorola 68HC11 Programmers Model

• Stack Pointer
• SP
• 16-bit registers pointing to the next available
  memory location for a push operation.
• Automatically decremented during a push
  operation, incremented during a pull operation.
• Must be initialized before use.

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Motorola 68HC11 Programmers Model

• Program Counter
• PC
• 16-bit register pointing to the beginning fot he
  next instruction to be executed.
• Automatically incremented after each instruction.
• Programmer has no control over, other than branch
  jump instructions.

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Motorola 68HC11 Programmers Model

• Condition Code Register
• CCR
• 4-bit register whose bits are set or reset during
  arithmetic or other operations.
• Used for branch operations.
• Bits include
• C Carry
• V Twos complements overflow
• Z Zero
• N Negative
• I Interrupt Mask
• H Half-carry
• X External Interrupt Mask
• S Stop Disable

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Motorola 68HC11 Programmers Model

• Condition Code Register Example
• ACCA ? F0
• ACCA ? ACCA F0
• 11110000
• 11110000
• 11100000
• C ? 1
• Z ? 0
• N ? 1
• V ? 0

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Addressing Modes

• Immediate Addressing
• ACCA ? 64
• Direct / Extended Addressing
• Direct Addr lt 0xFF
• Extended Addr gt 0x0100
• ADDA ? M(0064) (Direct)
• ADDA ? M(1234) (Extended)

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Addressing Modes

• Indexed Addressing
• ACCA ? M(IX 64)
• Inherent Addressing
• ADDA ? ACCA ACCB
• Relative Addressing
• PC ? (PC 15)

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Motorola 68HC11 Instruction Types

• Load Store Instructions
• 8-bit Load/Store
• 16-bit Load/Store
• Stack Push/Pull
• Transfer Register Instructions
• Decrement Increment Instructions

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Motorola 68HC11 Instruction Types

• Clear Set Instructions
• CLRA, CLRB, BCLR, BSET
• Shift Rotate Instructions
• Logical Shift
• Arithmetic Shift
• Rotate

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Motorola 68HC11 Instruction Types

• Arithmetic Instructions
• Add Subtract
• Decimal Instructions (BCD)
• Negating Instructions
• Multiplications
• Fractional Number Arithmetic
• Division

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Motorola 68HC11 Instruction Types

• Logic Instructions
• ANDA, ANDB, EORA, ORAA, COM
• Data Test Instructions
• BITA, BITB, CBA, CMPA, TST, TSTA
• Conditional Branch Instructions
• Signed Unsigned Conditional Branches
• BMI, BPL, BVS, GLT, BGT, BEQ, BNE
• Unconditional Jump Branch Instructions
• JMP, JSR, BSR, RTS BRA, BRN

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Motorola 68HC11 Instruction Types

• Condition Code Register Instructions
• CLC, SEC, CLV, CEV, TAP, TPA
• Interrupt Instructions
• CLI, SEI, RTI, SWI, WAI
• Miscellaneous Instructions
• NOP, STOP, TEST

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Assembly Language Overview
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Language Spectrum

• Machine Language
• Assembly Language
• Compiled Languages
• C, C, Pascal,
• Interpreted Languages
• Perl, TCL, UNIX shells
• Higher level Languages
• SQL, Etc

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Machine Language

• The lowest level of programming languages
• Binary encodings of the machines instructions
• Specific to the microprocessors
• Programmers do not write machine language
  programs (anymore)
• Machine language (or machine code) is
  automatically generated from the assembly or
  compilation processes

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Machine Language Example

• X ? 1234 (Immediate)
• LDX 1234
• ce 12 34
• X ? 1234 (Direct)
• LDX 1234
• fe 12 34

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Assembly Language

• One-to-one with Machine Language instructions
  (more or less)
• More legible
• Basic features
• One instruction per line.
• Labels provide names for addresses (usually in
  first column).
• Instructions often start in later columns.
• Columns run to end of line.

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Assembly Language

• Assembly languages are unique to each
  microprocessor.
• They are categorized at a much lower level than
  the High-Level Languages (HLLs)
• May not be executed on other computer systems
  with different microprocessors (unless the
  microprocessors are designed to be compatible)

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Assembly Language Examples

• Intel 8085, 8086, 80286,80486
• Intel Pentium
• Motorola 6800, 6805, and 6809
• Motorola 68000, 68020 68040
• Motorola PowerPC
• SUN Sparc processor

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Assembling Process

• When a programmer writes a program in assembly
  language, a specific assembler must be used to
  create the object code for that specific
  microprocessor
• The final executable file produced from this
  process can only be executed on a computer
  containing that specific type of microprocessor

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Assembling Process

• Major tasks
• generate binary for assembly instructions
• translate labels into addresses
• handle assembler directives
• Generally one-to-one translation.
• We are using a cross assembler
• Runs on a PC, but assembles for a 68HC11
• The assembler were using is an absolute
  assembler
• All source code must be in one file or group of
  files assembled together.

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Compilation Process

• Converts from a high level language to
  machine-executable machine language.
• Output format is called object code.
• Still needs to be linked before it can really be
  machine code.
• Some compilers provide a post-compilation
  assembly file or list file for debugging.

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Data Types

• Numeric Data
• Integers
• Fixed Point
• Floating Point
• Boolean Data
• TRUE 0
• Character Data
• American Standard Code for Information
  Interchange (ASCII)
• Extended Binary Coded Decimal Interchange Code
  (EBCDIC)
• UNICODE (Used extensively by Java)

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Programming in Assembly Language
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Assembly Fields

• This is a Comment!
• Label OPCODE OP1,OP2 Comment
• OPCODE OP1
• OPCODE Another Comment

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Labels

• A-Z a-z 0-9 . _
• Up to 15 characters
• 1st character can not be 0-9 or
• Case sensitive
• May end with
• May be on a line by itself.
• Examples
• Test
• _Test
• JumpToHere LDX 1234
• Label1

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Op-Codes

• Processor Instruction or
• Assembler Directive (pseudo-op)
• Must be preceded by at least one whitespace.
• JumpToHere LDX 1234
• JMP JumpToHere

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Operand Field

• Defines the operand for the instruction or
  directive.
• Depends on the instructions.
• Determines the addressing mode
• Can be expressions to be evaluated by the
  assembler.
• JumpToHere LDX 1234 5
• JMP JumpToHere

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Operand Field Addressing Modes

• Inherent
• INX
• Direct, Extended, Relative
• LDX 1234
• Immediate
• LDX 1234
• Indexed
• CLR 1234,X

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Comments

• Complete Line Comments First chararcter is an
  asterisk.
• This is a Comment
• Kent Orthner, May 22, 2003
• After the Operand
• JumpHere LDX 1234 5
• JMP JumpHere Also a Comment

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Hello World Example

• Hello World
• Kent Orthner, May 22, 2003
• Definitions
• OUTSTR EQU FFCA Define OUTSTR Function
• EOT EQU 04 Define EndOfText Char
• PROG EQU C000 Define Program Location
• STACK EQU DFFF Define Stack Location

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Hello World Example

• Program
• ORG PROG Locate program in mem
• lds STACK Init stack pointer
• ldx HELLO Point to start of message
• jsr OUTSTR Jump to print subroutine
• swi Returns to the debugger
• String Definition
• HELLO FCC /Hello World!/
• FCB EOT

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Assembler OutputMachine Language

• Addr Value
• c000 8e df ff ce
• c004 c0 0a bd ff
• c008 ca 3f 48 65
• c00c 6c 6c 6f 20
• c010 57 6f 72 6c
• c014 64 21 04

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Assembler Output List Files

• Line Addr Code Label Opcode
• 0001 Hello World
• 0002 Kent Orthner, May 22, 2003
• 0003
• 0004 Definitions
• 0005 ffca OUTSTR EQU FFCA Define
  OUTSTR
• 0006 0004 EOT EQU 04 Define
  EndOfTex
• 0007 c000 PROG EQU C000 Define
  Program L
• 0008 dfff STACK EQU DFFF Define
  Stack Lo

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Assembler Output List Files

• Line Addr Code Label Opcode
• 0009 Program
• 0010 c000 ORG PROG Locate
  program
• 0011 c000 8e df ff lds STACK Init
  stack po
• 0012 c003 ce c0 0a ldx HELLO Point to
  start
• 0013 c006 bd ff ca jsr OUTSTR Jump to
  print
• 0014 c009 3f swi Returns
  to the
• 0015
• 0016 String Definition
• 0017 c00a 48 65 6c HELLO FCC /Hello World!/
• 6c 6f 20
• 57 6f 72
• 6c 64 21
• 0018 c016 04 FCB EOT

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Instructions
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Assembler Directives
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Assembler Directives

• ORG Set the Program Counter
• ORG E000
• EQU Define Constants
• RAM EQU E000
• RMB Reserve Memory Bytes
• TABLE RMB 100

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Assembler Directives

• BSZ/ZMB Block Storage Zeroes
• ZeroSpace BSZ 100
• FCB Form Constant Byte
• CountSpace FCB 1,2,3,4,5,6
• FCC Form Constant Character String
• StringSpace FCC Hello World!

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Assembler Directives

• FDB Form Double Byte
• FDB 1234
• FILL Fill Memory
• AASpace aa,100
• OPT Assembler Output Options
• OPT c,l,cre

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Assembler Exercise
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Lab 1 Simple Menu
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Lab 1 Simple Menu

• Purpose
• Program assembly execution.
• Serial Input and Output.
• Polling-based timing.
• Parallel I/O
• Assignment
• Menu-based system.
• Control something with the Parallel I/O block.

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Lab 1 Simple Menu

• Criteria
• Serial output to display menu.
• Key entry causes menu change.
• 2-Level menu
• Pressing a key at the second level menu causes an
  external effect.
• Idiot-proof (Doesnt do anything when a wrong
  key is pressed.)

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Lab 1 Simple Menu

• Criteria
• Serial output to display menu.
• Key entry causes menu change.
• 2-Level menu
• Pressing a key at the second level menu causes an
  external effect.
• Idiot-proof (Doesnt do anything when a wrong
  key is pressed.)

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Lab 1 Simple MenuImplementation Hints

• Use Putchar(), Putstr(), getchar()
• Well cover how to create them next week.
• Suggested program flow
• Top Print Menu
• Wait for input
• Go to SubMenu1, submenu2, or top.
• Submenu1 Print submenu1
• wait for input
• Dosomething1, submenu1, or top.
• Dosomething1 Do the action.
• Go to Submenu1
• Submenu2