Slide 1'&$%ECE/CE 3720: Embedded System DesignChris J. MyersLecture 1: Microcomputer-Based SystemsSlide 2'&$%Embedded Computer Systems• An embedded computer system is a system that includes amicrocomputer configured to perform a dedicated application.• Software is typically fixed into ROM and not user accessible.• Microcomputer is embedded, or hidden, inside the device.• Typical automobile contains an average of 10 microcomputers.• Upscale homes may have as many as 150 microcomputers.• Average consumer interacts with µ-controllers 300 times/day.1Slide 3'&$%Examples of Embedded Computer SystemsSlide 4'&$%Examples of General-Purpose Computer Systems2Slide 5'&$%Real-Time Interfacing• Microcomputers accepts inputs, perform calculations, andgenerate outputs.• Real-time systems have an upper bound on the time requiredto perform the input/calculation/output sequence.• Must learn features built into microcomputers to handle time.• An interface is the hardware and software that allow thecomputer to communicate with the external hardware.• Must learn how to interface many types of inputs and outputsin both digital and analog form.Slide 6'&$%Chip Peripherals and Timer Features• Microcontrollers support many I/O features:– Synchronous Serial Peripheral Interface (SPI)– Asynchronous Serial Communication Interface (SCI)– Analog-to-digital (ADC) converters– Fixed period rate interrupts– Computer Operating Properly (COP) protection– Pulse accumulator for external event counting– Pulse-width-modulations (PWM) outputs– Event counter system for advanced timer operations– Input capture used for period and pulse width measurement– Output capture used for generating signals and frequencymeasurement3Slide 7'&$%Microcomputer ArchitecturesCompany ProductsMotorola 68HC05, 68HC08, 68HC11, 68HC12, 68HC16,68K, MCORE, Coldfire, PowerPCIntel 8051, 80251, 8096, 80296Philips 8051Hitachi H8NEC 78KMitsubishi 740, 7600, 7700, M16CSiemens C500, C166, TricoreMicrochip PIC12, PIC16, PIC17Slide 8'&$%Choosing a Microcomputer• Many factors to consider when selecting a microcomputer:– Labor, material, manufacturing, maintenance costs.– ROM, RAM, and EEPROM size.– Speed and I/O bandwidth requirements for application.– 8-,16-, or 32-bit data size.– Numerical or other special operations required.– Number of parallel and serial ports needed.– Timer, PWM, and ADC requirements.– Package size and environmental issues.– Second source availability.– Availability of compilers, simulators, and emulators.– Power requirements.4Slide 9'&$%MC68HC11 Architecture• CPU optimized for low power and operation up to 4 MHz.• Uses either two separate 8-bit accumulators (A,B) or onecombined 16-bit accumulator (D).• Has two 16-bit index registers (X,Y).• Has powerful bit-manipulation instructions.• Supports 16-bit add/subtract, 16 × 16 integer divide, 16 × 16fractional divide, and 8 × 8 unsigned multiply.• Lends itself to C compiler implementations.Slide 10'&$%MC68HC11 Family• A series - basic model.• D series - economical alternative, less memory, peripherals.• E series - has wide range of I/O capabilities.• F series - higher speed, extra I/Os.• G series - 10-bit ADC and better timer systems.• K series - high speed, larger memories, MMU, and PWM.• L series - high speed, low power, static design.• M series - has math coprocessor and four channel DMA.• P series - power-saving PLL and 3 SCI ports.5Slide 11'&$%MC68HC11E Block DiagramSlide 12'&$%Operating Modes• The 6811 can operate in one of four modes:– Single-chip mode uses internal memory for program & data.– Expanded mode allows for use of external memory.– Bootstrap mode used to load programs into RAM.– Test mode used by Motorola to test the chip is operational.6Slide 13'&$%Address Map for MC68HC11E1CP2Address (hex) Size Device Contents0000 to 01FF 512 RAM Variables and stack1000 to 103F 64 I/OB600 to B7FF 512 EEPROM Program and constantsSlide 14'&$%MC68HC11 Registers7Slide 15'&$%Assembly Language• Assembly language instructions have four fields:Label Opcode Operand(s) Commenthere ldaa 100 RegA = [100]• Assembly instructions are translated into machine code:Object code Instruction Comment$86 $64 ldaa 100 RegA = [100]Slide 16'&$%MC68HC11 Addressing Modes• Inherent addressing mode• Immediate addressing mode• Direct page addressing mode• Extended addressing mode• Indexed addressing mode• PC relative addressing mode8Slide 17'&$%Inherent Addressing Mode• Has no operand field.Obj code Op Comment$3D mul RegD = RegA * RegB$02 idiv RegX = RegD / RegXRegD=remainder$03 fdiv RegX = (65536 * RegD)/RegX,RegD=remainder$1808 iny RegY = RegY + 1$3F swi Software interrupt$1B aba RegA = RegA + RegB$0E cli Condition Code I bit = 0$3A abx RegX = RegX + RegBSlide 18'&$%Immediate Addressing Mode• Uses a fixed constant.• Data is included in the machine code.Obj code Op Operand Comment$8E00FF lds #$00FF Initialize stack$8900 adca #0 RegA = RegA + C$C880 eorb #$80 Invert bit 7 of RegB$8A02 oraa #2 Set bit 1 of RegA9Slide 19'&$%Direct Page Addressing Mode• Uses an 8-bit address to access from addresses 0 to $00FF.Obj code Op Operand Comment$9632 ldaa 50 RegA = [$0050]$9D64 jsr 100 Jump to sub at loc 100$DF34 stx <$1234 [$0034] = RegX$150A03 bclr 10 3 Clr bits 1,0 of loc 10$140A81 bset 10 $81 Set bits 7,0 of loc 10Slide 20'&$%Extended Addressing Mode• Ues a 16-bit address to access all memory and I/O devices.Obj code Op Operand Comment$B71004 staa $1004 [$1004] = RegA$FE8000 ldx $8000 RegX = [$8000]$BF9000 sts $9000 [$9000] = RegSP$B60000 ldaa >0 Force 16-bit address10Slide 21'&$%Indexed Addressing Mode• Uses an 8-bit unsigned offset with either RegX or RegY.Obj code Op Operand Comment$A704 staa 4,X [X+4] = RegA$CE1000 ldx #$1000 RegX points tointernal I/O block$1D0313 bclr 3,X,%00010011 Clear Port C,bits 4,1,0$18CE100E ldy #$100E RegY points to TCNT$18EC00 ldd ,Y Read TCNT ($100E)into RegDSlide 22'&$%PC Relative Addressing Mode• Used for branch and branch-to-subroutine instructions.• Assume branch located at $F880.Obj code Op Operand Comment$8105 cmpa #5 Compare RegA to 5$25BE blo $F840 goto $F840 if RegA<5$20BE bra $F840 goto loc $F840$8D46 bsr $F8C8 goto to sub at $F8C8$12051005 brset 5,$10,$F889 goto $F889 ifbit 4 of loc 5 is 111Slide 23'&$%References (all linked on course website)• Motorola 68HC11 Reference Manual• Motorola 68HC11E Family Data Sheet• Motorola 68HC11