Microprocessor and Microcontroller - Lec 1 - Google Sites

Microcontroller Based Design Muhammad Usman Rafique

Week 5 – Timers and Counters

2

M. Usman Rafique

Air University, Spring 2015

Course Outline Week 1

Introduction

2

8051Microcontroller  Architecture and Hardware

3



Assembly Language

4



Assembly Language Contd.

5



Timers and Counters

6



Serial Port

7



Interrupt

8, 9



Design and Interface Examples

10

Midterm Exam

11

PIC 18 F Microcontroller  Introduction, Architecture, I/O Pins

12



Programming in C

13



Timers / Counters

14



Using Internal ADC of PIC

15, 16



Peripherals of PIC 18F Microcontrollers

17

3

Topic

Revision

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Organization 

Introduction



Timers 



Delay Generation Measuring Time

Counters



4

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Timers and Counters 2 Timers in 8051







T0 T1

Timers can be used to 1. Measure time between events 2. Generate required amount of time 3. Count events 4. Generate baud rate for Serial communication 

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Timers and Counters Modes of operation are 2 Timers

Timers

Measure Time

6

Counters

Serial Port

Generate Time

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Timers and Counters Always counts up in any operational mode







Timer Counter

Timer





Timer increments by 1 every machine cycle

Counter





Increments at every input pulse

Time of 1 Machine Cycle, for 12 MHZ crystal? 1 micro second for crystal of 12 MHz 7

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Timers and Counters Time of 1 Machine Cycle for 11.0592 MHz crystal?  Oscillator (Crystal) : 11.0592 MHz 12 Clock cycles make 1 Machine cycle



1 Machine Cycle = 12 Clock cycles 

Time of 1 clock cycle = 1 / 11.0592M



Time of 1 Machine Cycle = 12* (1 / 11.0592M ) 1 Machine Cycle 8

= 1.0851 Micro Seconds M. Usman Rafique


Timers and Counters Timer SFRs

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Timers and Counters Timer SFRs

10

SFR

Timer

Description

TMOD

T0 and T1

Set Timer Mode

TCON

T0 and T1

Control Timer Operation

TL0

T0

Timer 0 Low Byte

TH0

T0

Timer 0 High Byte

TL1

T1

Timer 1 Low Byte

TH1

T1

Timer 1 High Byte

M. Usman Rafique


Timers and Counters 

Separate Registers – TH and TL  

High and Low byte of Timer Timer 0: TH0 (1 Byte)

TL0 (1 Byte) TIMER 0



Timer 1: TH1 (1 Byte)


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Timers and Counters Configuring Timers TMOD

12

Bit

Name

Explanation of Function

Timer

GATE1

= 1 Timer will only run when INT1 is high. (Calculate Time between events) = 0 for Timer1

1

6

C/T1

=1 Input on P3.5 drives time. Counter Mode = 0 Crystal drives Timer. Timer Mode

1

5

T1M1

Timer mode bit

1

4

T1M0

Timer mode bit

1

3

GATE0


0

2

C/T0

=1 Counter = 0 Timer

0

1

T0M1

Timer mode bit

0

0

T0M0

Timer mode bit

0

7

Timers and Counters

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Timers

14

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Timers and Counters Modes of operation are 2 Timers

Timers

Measure Time

15

Counters

Serial Port

Generate Time

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Timers 

Timer Operation 1. 2. 3.

16

Configure timers (TMOD) Initialize values (TH and TL) Start and Stop Timer (TCON)

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Timers Using 8051 Timers 



TH0 (1 Byte)

TH and TL contain the ‘value’ of timer Timers count UP. This value will be incremented by 1 every machine cycle


TH1 (1 Byte)




When TH and TL have maximum value, next machine cycle would set them both to ZERO.



Practice 

17

What is the maximum value TH and TL (1 Byte each) can have?

M. Usman Rafique


Timers Using 8051 Timers TH0 (1 Byte)



What is the maximum value TH and TL (1 Byte each) can have?



Maximum value = 1111 111 1111 1111 TH



18


TL

= FF FF = 65,535

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Timers Using 8051 / 8052 Timers  Maximum value of Timer Registers= FF FF = 65,535

Timer Operation

TH0 (1 Byte)


Timer Value (TH , TL)

Time 19

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Timers Timer Modes    

20

Mode 0 – 13 Bit Timer Mode 1 – 16 Bit Timer Mode 2 – 8 Bit Timer Mode 3 – Split Timer

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Timers Timer Modes Mode 0 – 13 Bit Timer





To keep compatibility with 8048 (old) TL counts 0 to 31 From 31, TL resets to ZERO and increments TH by 1



Not used generally

 

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Timers Timer Modes 65,535d FF FFh

Mode 1 – 16 Bit Timer

 

Commonly used Counts up to FF FF and resets to zero



Working: as discussed previously



Timer Value (TH , TL)

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Timers Timer Modes Mode 2 – 8 Bit Timer

   

8 Bit Auto-Reload Mode TH = Reload value TL = Time Value Timer Value

Reset Reload Value

Time 23

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Timers Timer Modes Mode 3 – Split Timer

   



 

24

When Timer 0 is placed in mode 3, it becomes 2 x 8 bit Timers Timer 0 is TL0 Timer 1 is TH0 Bits of Timer1 are related to TH0 Timer 1 can be in mode 0,1 or 2. Timer 1 will be incremented every machine cycle in any case – no control

M. Usman Rafique


Timers Configuring Timers TMOD

25

Bit

Name


Timer

GATE1


1

6

C/T1

=1 Input on P3.5 drives time. Counter Mode = 0 Crystal drives Timer. Timer Mode

1

5

T1M1

Timer mode bit

1

4

T1M0

Timer mode bit

1

3

GATE0


0

2

C/T0


0

1

T0M1

Timer mode bit

0

0

T0M0

M. Usman Timer mode bit Rafique

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Air University, Spring02015

Timers Configuring Timers TMOD Timer Mode TxM1

26

TxM0

Timer Mode

Description of Mode

0

0

0

13-bit Timer.

0

1

1

16-bit Timer

1

0

2

8-bit auto-reload

1

1

3

Split timer mode

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Bit

Name


Timer

7

GATE1

= 1 for External Time Measurement = 0 for Timer 1

1

6

C/T1


1

5

T1M1

Timer mode bit

1

4

T1M0

Timer mode bit

1

3

GATE0

= 1 for External Time Measurement = 0 for Timer 0

0

Description of Mode

2

C/T0


0

Timers Configuring Timers TMOD Practice 



Timer 0 in Mode 1 Timer 1 in Mode 2 Timer Mode

TxM1

TxM0

0

0

0

13-bit Timer.

1

T0M1

Timer mode bit

0

0

1

1

16-bit Timer

0

T0M0

Timer mode bit

0

1

0

2

8-bit autoreload

1

1

3

Split timer mode

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Timers Configuring Timers TMOD  

Timer0 in Mode1 Timer1 in Mode3

MOV tmod,#00100001b OR MOV tmod,#21h 28

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Timers Controlling Timers TCON Bit

Name


Timer

7

TF1

Timer 1 Overflow. = 1 when T1 Overflows

1

6

TR1

Timer 1 Run. = 1 Timer1 Runs = 0 Timer 1 Stops

1

5

TF0

Timer 0 Overflow. = 1 when T0 Overflows

0

TR0

Timer 0 Run. = 1 Timer0 Runs = 0 Timer 0 Stops

0

4

Lower Bits are related to Interrupts and will be covered later on 29

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Timers Controlling Timers TCON setb tr0

;running the timer

Label: JNB tf0, Label

; waiting till overflow flag is set

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Timers Using 8051 / 8052 Timers 

How to run timers for a given time?



How to measure time between 2 events?

31

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How to run timers for a given time?

2 Timers

Timers

Measure Time 32

Counters

Serial Port

Generate Time M. Usman Rafique



1. 2. 3.

33

How to run timers for a given time? Select Timer Mode – TMOD Store a Value in Timer Register – TH and TL Wait for Timer to Over-flow or Reset – TCON

M. Usman Rafique



1. 2.

How to run timers for a given time? Select Timer Mode Set an appropriate Value in Timer Register Timer Value = 65536 – (Desired Number of Machine Cycle) Value

Reset

Timer Value

34

Time

Timers Practice  Set P3.0 high for 0.05 seconds using Timer 0

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Timers 

Set P3.0 high for 0.05 seconds using Timer 0



Finding Value of Timer 

0.05 sec = 50,000 micro seconds



1.0851 micro sec 1 micro sec 50,000 micro sec

 

36

= 1 Machine Cycle = (1 / 1.0851) Machine Cycles = 50,000 * (1/1.0851) = 46079 Machine Cycles

M. Usman Rafique


Timers Using 8051 / 8052 Timers  Set P3.0 high for 0.05 seconds using Timer 0 Value to load in TH and TL? 

Timer Value = 65536 – (Desired Number of Pulses) = 65536 – 46079 = 19456 = 4C 01h



TH = 4Ch ; TL = 01h

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Timers Using 8051 / 8052 Timers  Set P3.0 high for 0.05 seconds using Timer 0 Timer Mode  Mode 1 = 16 Bit timer Mode can be used  TMOD = 0000 0001b T1 T0

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Timers Using 8051 / 8052 Timers  Set P3.0 high for 0.05 seconds using Timer 0 MOV TMOD,#00000001b; MOV TH0,#4Ch; MOV TL0,#01h; setb P3^0 setb TR0

Here: JNB TF0, Here CLR P3^0 39

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Timers 


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2 Timers

Timers

Measure Time 41

Counters

Serial Port

Generate Time M. Usman Rafique


Timers 

How to measure time between 2 events? 

42

Set GATE Bit in TMOD

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Timers 

43


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Timers 


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Timers 




Set GATE Bit in TMOD C / T = 0 to ensure that crystal is connected to timers



When TR = 1, timer will run ONLY WHEN P3.2or P3.3 is set



So, timer value be corresponding to the time P3.2 or P3.3 remains high



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Counters

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Counters

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Counter Counter  

If TCON – Bit “C/T” = 1 Timer runs as counter



Timer 0 – Pin 3.4 (T0) Timer 1 – Pin 3.5 (T1)



Events (pulses) on these pins will be counted



Frequency consideration



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Counter Counter 

Value of Timer is incremented by 1 when there is 1-to-0 (High to Low) transition on the pin



For counter to count, there must be 1 during one machine cycle and 0 during next machine cycle



Maximum frequency: 2 machine cycles = 2 micro sec (for 12 MHz crystal) Frequency = 500 kHz 49

M. Usman Rafique


Acknowledgement Material used with permission of 

Dr. Javaid Iqbal 



Head of Department, Mechatronics Engineering College of EME, NUST

I am extremely thankful to Dr. Javaid who has been a great teacher and still helps and supports me

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