UBC104 Embedded Systems. Review: Introduction to Microcontrollers

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1 UBC104 Embedded Systems Review: Introduction to Microcontrollers

Processors General purpose processors: 80386 Pentium Core Duo Large number of pins External

2 Processors General purpose processors: Pentium Core Duo Large number of pins External memory External peripherals * Figure from Intel 386 DX Datasheet UBC 104 Embedded Systems 2

3 General Purpose Registers Registers are dedicated for moving data EAX, EBX, ECX, EDX: general purpose registers EBP: Base pointer ESP: Stack pointer ESI, EDI: Index register UBC 104 Embedded Systems 3

4 Microcontrollers Support for peripherals inside ucontroller Limited number of pins Dedicated purpose Controlling devices, taking measurements Controller families: 68H12: Motorola 68H11, 68HC12, 8051: Intel 8051, 8052, 80251, PIC: Microchip PIC16F628, 18F452, 16F877, AVR: Atmel ATmega128, ATtiny28L, AT90S8515, UBC 104 Embedded Systems 4

Rita51J 8051 128K of SRAM 128K FLASH ROM Serial port Digital I/O

5 Rita51J K of SRAM 128K FLASH ROM Serial port Digital I/O lines * Figure from UBC 104 Embedded Systems 5

6 Motes Sensor nodes based on Atmel ATMega128 * Figures from CrossbowMPR-MIBUser Manual UBC 104 Embedded Systems 6

18F452, 16F877, AVR: Atmel ATmega128, ATtiny28L,

7 Microcontroller Families 68H12: Motorola 68H11, 68HC12, 8051: Intel 8051, 8052, 80251, PIC: Microchip PIC16F628, 18F452, 16F877, AVR: Atmel ATmega128, ATtiny28L, AT90S8515, We are going to look at 8051s UBC 104 Embedded Systems 7

8 Typical 8051s 32 input / output lines. Internal data (RAM) memory bytes. Up to 64 kbytes of ROM memory (usually flash) Three 16-bit timers / counters 9 interrupts (2 external) with two priority levels. Low-power Idle- and Power-down modes UBC 104 Embedded Systems 8

9 Datasheets Your New Friends! * Figure from Atmel AT89C51RD2 Datasheet UBC 104 Embedded Systems 9

10 Pin-Out of an 8051 UBC 104 Embedded Systems 10

11 8051 Components Ports RAM Interrupt Controller Timer SPI Controller * Figure from Atmel AT89C51RD2 Datasheet UBC 104 Embedded Systems 11

12 8051 Internal RAM & SFRs * Figure from Atmel AT89C51RD2 Datasheet UBC 104 Embedded Systems 12

13 Special Function Registers (SFR) * Figure from Atmel AT89C51RD2 Datasheet UBC 104 Embedded Systems 13

14 Special Function Registers (SFR) * Figure from Atmel AT89C51RD2 Datasheet UBC 104 Embedded Systems 14

15 * Figure from Atmel AT89C51RD2 Datasheet UBC 104 Embedded Systems 15

16 Ports Driving low-power peripherals ie. LEDs, relays UBC 104 Embedded Systems 16

17 Accessing Ports in C void main (void) { unsigned int i; /* Delay var */ unsigned char j; /* LED var */ while (1) { /* Loop forever */ for (j=0x01; j< 0x80; j<<=1) { /* Blink LED 0, 1, 2, 3, 4, 5, 6 */ P1 = j; /* Output to LED Port */ for (i = 0; i < 10000; i++) { /* Delay for Counts */ wait (); /* call wait function */ } } for (j=0x80; j> 0x01; j>>=1) { /* Blink LED 6, 5, 4, 3, 2, 1 */ P1 = j; /* Output to LED Port */ for (i = 0; i < 10000; i++) { /* Delay for Counts */ wait (); /* call wait function */ } } } } UBC 104 Embedded Systems 17

18 Summary General information about 8051 Special Function Registers (SFRs) Control of functionality of ucontroller Ports Input/Output of ucontroller UBC 104 Embedded Systems 18

19 UBC104 Embedded Systems Motivation for Next Topics

20 Tasks for Microcontroller Controlling of processes (autonomic) e.g. speed of vehicles, chemical processes Control of devices through human operator e.g. remote control, etc UBC 104 Embedded Systems 20

21 Example: Controller Engineering UBC 104 Embedded Systems 21

22 Topics for the Following Lectures Interrupts & Timers Communication Analog to digital (A/D) conversation Pulse Width Modulation UBC 104 Embedded Systems 22

23 UBC104 Embedded Systems Interrupts & Timers

24 Today s Topics Interrupts Timers UBC 104 Embedded Systems 24

25 Interrupts Definition of Interrupt Event that disrupts the normal execution of a program and causes the execution of special instructions UBC 104 Embedded Systems 25

26 Interrupts Program time t UBC 104 Embedded Systems 26

27 Interrupts Interrupt Program time t UBC 104 Embedded Systems 27

28 Interrupts Interrupt Program Program Interrupt Service Routine time t UBC 104 Embedded Systems 28

29 Interrupt Handling Address space in code space Code that deals with interrupts: Interrupt Handler or Interrupt Service Routines (ISRs) UBC 104 Embedded Systems 29

30 Interrupt Handling Code that deals with interrupts: Interrupt Handler or Interrupt Service Routines (ISRs) Possible code: Interrupt number void ISR(void) interrupt 1 { } ++interruptcnt; UBC 104 Embedded Systems 30

Interrupts fahr= (cent * ) +32 9 5 Interrupt Program mov R1, cent mul

31 Interrupts fahr= (cent * ) Interrupt Program mov R1, cent mul R1, 9 div R1, 5 add R1, 32 mov fahr, R1 time t UBC 104 Embedded Systems 31

32 Interrupts Interrupt Program Program mov R1, cent mul R1, 9 Interrupt Service Routine mov R1, 0x90 mov sensor, R1 ret time t UBC 104 Embedded Systems 32

33 Interrupts Interrupt Program Program Save Restore mov R1, cent mul R1, 9 Context Interrupt Context Service Routine time t UBC 104 Embedded Systems 33

34 Interrupts Interrupt Program Program Save Restore mov R1, cent mul R1, 9 Context Interrupt Context eg push R1 Service eg pop R1 Routine time t UBC 104 Embedded Systems 34

35 Interrupt Overheads Interrupt arrives Complete current instruction Save essential register information Vector to ISR Save additional register information Interrupt Latency Execute body of ISR Restore other register information Return from interrupt and restore essential registers Resume task Interrupt Termination UBC 104 Embedded Systems 35

36 Interrupt Response Time Interrupt Latency Interrupt Response Time= Interrupt Latency + Time in Interrupt Routine UBC 104 Embedded Systems 36

37 Interrupts Internal or External Handling can be enabled/disabled Prioritized General 8051: 3x timer interrupts, 2x external interrupts 1x serial port interrupt UBC 104 Embedded Systems 37

38 Interrupt Priorities Each interrupt source has an inherent priority associated with it UBC 104 Embedded Systems 38

39 Interrupt Priorities Priorities can be adapted by programs Original 8051 provides 1- bit per interrupt to set the priority UBC 104 Embedded Systems 39

40 2-bit Interrupt Priorities The 89C52RD2 provides 2bit-interrupt priorities UBC 104 Embedded Systems 40

41 2-bit Interrupt Priorities (continued) UBC 104 Embedded Systems 41

42 2-bit Interrupt Priorities (continued) UBC 104 Embedded Systems 42

43 External Interrupts Pins for external interrupts UBC 104 Embedded Systems 43

44 External Interrupts External Interrupts: Level- or edge-triggered UBC 104 Embedded Systems 44

45 External Interrupts External Interrupts: Level- or edge-triggered Level-triggered threshold trigger point t UBC 104 Embedded Systems 45

46 External Interrupts External Interrupts: Level- or edge-triggered Level-triggered threshold trigger point t Edge-triggered trigger point t UBC 104 Embedded Systems 46

47 Timer A timer is a counter that is increased with every time an instruction is executed e.g with 12MHz increases a counter every µs General 8051 has 3 timer: 2 16-bit timer 1 16-bit timer with extrafunctionality (introduced with the 8052) Timer/Counter Mode Control Register TMOD Timer/Counter Control Register TCON UBC 104 Embedded Systems 47

48 Timer High- & Low-Registers UBC 104 Embedded Systems 48

49 SFR Map Timer Registers UBC 104 Embedded Systems 49

50 Timer Control Timer/Counter Mode Control Register TMOD Timer/Counter Control Register TCON UBC 104 Embedded Systems 50

51 SFR Map Timer Control UBC 104 Embedded Systems 51

52 SFR Map Timer 2 UBC 104 Embedded Systems 52

53 Timer Code void TimerInit(void) { // Timer 2 is configured as a 16-bit timer, // which is automatically reloaded when it overflows // This code (generic 8051/52) assumes a 12 MHz system osc. // The Timer 2 resolution is then µs // Reload value is FC18 (hex) = (decimal) // Timer (16-bit) overflows when it reaches (decimal) // Thus, with these setting, timer will overflow every 1 ms T2CON = 0x04; // Load Timer 2 control register TH2 = 0xFC; // Load Timer 2 high byte RCAP2H = 0xFC; // Load Timer 2 reload capt. reg. high byte TL2 = 0x18; // Load Timer 2 low byte RCAP2L = 0x18; // Load Timer 2 reload capt. reg. low byte } ET2 = 1; TR2 = 1; // Enable interrupt // Start Timer 2 running UBC 104 Embedded Systems 53

54 Interrupt Code for Timer 2 void handletimer2 (void) interrupt 5 { /* execute interrupt code */ } UBC 104 Embedded Systems 54

55 Interrupt Flags Bits that are set if the interrupt occurs UBC 104 Embedded Systems 55

56 Code for Interrupt Flags /* Configure Timer 0 as a 16-bit timer */ TMOD &= 0xF0; /* Clear all T0 bits (T1 left unchanged) */ TMOD = 0x01; /* Set required T0 bits (T1 left unchanged) */ ET0 = 0; /* No interrupts */ /* Values for 50 ms delay */ TH0 = 0x3C; /* Timer 0 initial value (High Byte) */ TL0 = 0xB0; /* Timer 0 initial value (Low Byte) */ TF0 = 0; /* Clear overflow flag */ TR0 = 1; /* Start Timer 0 */ while (TF0 == 0); /* Loop until Timer 0 overflows (TF0 == 1) */ TR0 = 0; /* Stop Timer 0 */ UBC 104 Embedded Systems 56

57 Summary: Interrupts Definition of Interrupt : Event that disrupts the normal execution of a program and causes the execution of special instructions Handling can be enabled/disabled Prioritized Internal or External External Interrupts: Level-triggered Edge-triggered 8051: 3 timer interrupts, 2 external interrupts & a serial port interrupt Level-triggered trigger point Edge-triggered trigger point threshold t t UBC 104 Embedded Systems 57

58 Real-Time Systems Definition: A real-time system needs to be predictable in terms of values and time Correctness of an RT system depends on functionality as well as temporal behaviour UBC 104 Embedded Systems 58

59 Clock Driven Scheduling Decision on what job execute are made at specific time instants chosen a priori before the system starts operation A schedule of jobs is created off-line and used at run time The scheduler dispatches jobs according to the stored schedule at each scheduling decision time Clock-driven scheduling has minimal overhead during run time No interrupt Start Invoke Scheduler Pick & dispatch a job Set timer Block waiting for timer interrupt Timer Interrupt Service Routime UBC 104 Embedded Systems 59

60 Cyclic Executive #define TASK_MAX 4 typedef void (func_ref)(void); int delay[task_max]; func_ref task_ref[task_max]; void cyclic_executive() { int task= 0; while(1) { settimer(delay[task]); taskref[task](); task= (task==task_max)? task+1 : 0; clear(time_flag); while (time_flag) enteridlemode(); } UBC 104 Embedded Systems 60

61 Cyclic Executive (continued) void timer(void) interrupt 5 { set(time_flag); } void EnterIdleMode(void) { PCON = 0x01; } Frame T delay,1 T 1 T 2 IdleMode T 3 T 1 T 2 T 3 t UBC 104 Embedded Systems 61

62 Problems with Cyclic Executives Timing Accuracy Actually constructing the cyclic executive (Typical realistic problem: 40 minor cycles and 400 entries) Inflexibility must reconstruct schedule even for minor changes Incorporating Aperiodic/Sporadic Tasks, or very long period tasks I/O only by polling UBC 104 Embedded Systems 62

63 General Embedded Programming Endless loops Idle mode for 8051 Generic main() function UBC 104 Embedded Systems 63

64 Endless Loops Two types of tasks: Run-To-Completion tasks Endless-Loop tasks UBC 104 Embedded Systems 64

65 Endless Loops Two types of tasks: Run-To-Completion tasks Endless-Loop tasks Interrupt handler are run-to-completion tasks The majority of generic tasks are endless loops UBC 104 Embedded Systems 65

66 Endless Loops Two types of tasks: Run-To-Completion tasks Endless-Loop tasks Interrupt handler are run-to-completion tasks The majority of generic tasks are endless loops Example Code: void ExampleTask(void) { } while(1) { waitforactivation; dotask; } UBC 104 Embedded Systems 66

67 Idle Mode 8051s implement an idle mode which consumes less power UBC 104 Embedded Systems 67

68 Idle Mode 8051s implement an idle mode which consumes less power UBC 104 Embedded Systems 68

69 Idle Mode 8051s implement an idle mode which consumes less power from Pont: Atmel 89S53 normal mode 11mA idle mode 2mA UBC 104 Embedded Systems 69

70 Idle Mode 8051s implement an idle mode which consumes less power from Pont: Atmel 89S53 normal mode 11mA idle mode 2mA Example Code: void EnterIdleMode(void) { PCON = 0x01; } UBC 104 Embedded Systems 70

71 Generic main() Function void main(void) { /* initialize system */ /* initialize tasks */ } while (1) { /* loop forever */ EnterIdleMode(); /* PCON = 0x01*/ } UBC 104 Embedded Systems 71

72 Summary Cyclic executives Endless loops Idle mode UBC 104 Embedded Systems 72

8051 Microcontroller

8051 Microcontroller The 8051, Motorola and PIC families are the 3 leading sellers in the microcontroller market. The 8051 microcontroller was originally developed by Intel in the late 1970 s. Today many