Chp7 pic 16 f84 interfacing - copy

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PIC 16F84 InterfacingPIC 16F84 Interfacing

I/O PortsI/O Ports

To be used as input or output Also being used for other

functions such as timer, interrupt and serial communication

Port A & TRISA Registers

BCF STATUS, RP0 CLR PORTA ; Initialize PORTA by

clearing ; output data latches

BSF STATUS, RP0 ; Select Bank 1MOVLW 0x0F ; Value used to initialize

data; direction

MOVWF TRISA ; Set RA<3:0> as inputs; RA4 as output; TRISA<7:5> are always; read as ’0’.


Block diagram of Pins RA3:RA0 Block diagram of Pin RA4


Inputting (Reading) 1 from a Pin the PIC16

1 1

0

x 1OFF

0

OFF

1

1

11

1

1

TRIS = 1


Inputting (Reading) 0 from a Pin the PIC16

1 1

0

x 1OFF

0

OFF

0

0

00

0

0

TRIS = 1


Outputting (Writing) 0 to a Pin in the PIC16

0 0

1

1 1OFF

1

ON

zero

0

TRIS = 0


Outputting (Writing) 1 to a Pin in the PIC16

0 0

1

0 0ON

0

OFF

one

1

TRIS = 0

Port B & TRISB Registers

BCF STATUS, RP0 ;CLRF PORTB ; Initialize PORTB by

clearing ; output data latches

BSF STATUS, RP0 ; Select Bank 1MOVLW 0xCF ; Value used to initialize

data; direction

MOVWF TRISB ; Set RB<3:0> as inputs; RB<5:4> as outputs; RB<7:6> as inputs

Port B & TRISB Registers

Block diagram of Pins RB7:RB4 Block diagram of Pin RB3:RB0

Interrupt

A mechanism that allows C responds to some events at the moment they occur, regardless of what C is doing at that time

Interrupt changes the program flow and invokes interrupt subroutine (Interrupt Service Routine, ISR)

INTCON is control register of interrupt

Interrupt Cont…

Interrupt Cont…

Interrupt sources: Termination of writing data to EEPROM TMR0 interrupt caused by timer overflow Interrupt during alteration on RB4, RB5, RB6

& RB7 of port B External interrupt from RB0/INT pin

INTCON Register

INT External Interrupt Enable

TMR0 Overflow Interrupt Enable

EEPROM Write Complete Interrupt Enable

Global Interrupt Enable

RB Port Change Interrupt Enable

TMR0 Overflow Interrupt Flag

INT External Interrupt Flag

RB Port Change Interrupt Flag

INTCON Register Cont…

EECON1

Interrupt Execution

GOTO YYY

Interruptserviceroutine

Mainprogram

000

004

XXXYYY

ZZZ

3FF

PCL

OPTION

INTCON

TMR0

EECON1

ZZZ

RB7RB6RB5RB4

RB0

Control

Program counter Stack

Example 7.1

The normal activity of program is to output binary count value on Port B. This process will be interrupted by RB0 that will be pulsed manually. The interrupt service routine causes all the outputs to be switched on, and waits for the button RA4 to be pressed. The routine then terminates by restoring the previous value in Port B data register and returns to the main program at the original point.

Example 7.1 cont…

INT1

Initialize ports and interrupt

Increment LEDs

Delay

Main Sequence

Delay

Load ‘timer’ register with FF

Decrement

‘timer’ zero ?

Return

Yes

No

Delay routine

No

Yes

Example 7.1 Cont…

ISR

Save current LEDs value

Switch on all LEDs

Restart input = 0?

Restore previous LEDs value

Re-enable interrupt

Return

A

A

Interrupt Service Routine

Yes

No

Example 7.1 Cont…

;Register Label Equates.......................................

PORTA EQU 05 ;Port A Data RegisterPORTB EQU 06 ;Port B Data RegisterINTCON EQU 0B ;Interrupt Control Registertimer EQU 0C ;GPR1 = delay countertempb EQU 0D ;GPR2 = Output temp. store

;Input Bit Equal Equates......................................

intin EQU 0 ;Interrupt input = RB0resin EQU 4 ;Restart input = RA4INTF EQU 1 ;RB0 Interrupt Flag

;*************************************************************;Set program origin for power On Reset........................

ORG 000 ;Program start addressGOTO setup ;Jump to main program start

Example 7.1 Cont…

;Interrupt Service Routine at address........................

ORG 004 ;ISR start address

MOVF PORTB,W ;Save current output valueMOVWF tempb ;in temporary register

MOVLW b'11111111' ;Switch LEDs 1-7 onMOVWF PORTB

wait BTFSC PORTA,resin ;Wait for restart inputGOTO wait ;to go low

MOVF tempb,w ;Restore previous outputMOVWF PORTB ;at the LEDsBCF INTCON,INTF ;Clear RB0 interrupt flag

RETFIE ;Return from interrupt

Example 7.1 Cont…

;DELAY subroutine................................................

delay MOVLW 0xFF ;Delay Count literal isMOVWF timer ;loaded into spare register

down DECFSZ timer ;Decrement timer registerGOTO down ;and repeat until zero thenRETURN ;return to main program

;Main Program***************************************************

;Initialize Port B (Port A defaults to inputs)..................

setup MOVLW b'00000001' ;Set data direction bitsTRIS PORTB ;and load TRISB

MOVLW b'10010000' ;Enable RB0 interrupt inMOVWF INTCON ;Interrupt Control Register

;Main output loop...............................................

count INCF PORTB ;Increment LED displayCALL delay ;Execute delay subroutineGOTO count ;Repeat main loop always

END ;Terminate source code

Interrupt on Pins RB4-RB7

Interrupt on Pins RB4-RB7 cont…

;PROGRAM INTPORTB.ASM

#INCLUDE "P16F84.INC"

ORG 0x00GOTO MainORG 0x04GOTO ISR

MainMOVLW 0xF0TRIS PORTBMOVLW 0xFFMOVWF PORTB ;Turn ON LEDBSF INTCON,GIEBSF INTCON,RBIE

LOOPGOTO LOOP

Interrupt on Pins RB4-RB7 cont…

ISR BCF INTCON,RBIF ;Clears the flag that indicates RB interrupt;took place thus enabling detection of new;new interrupts in main program

BTFSS PORTB,7 ;Determining which button caused the interruptGOTO LED0BTFSS PORTB,6GOTO LED1BTFSS PORTB,5GOTO LED2BTFSS PORTB,4GOTO LED3RETFIE

LED0 BCF PORTB,0 ;Switch off LED LD0RETFIE




END

Interrupt on Pin RB0

Interrupt on Pin RB0 cont…

;PROGRAM INTRB0.ASM

#include "P16F84.INC"

ORG 0x00GOTO MAINORG 0x04GOTO ISR

MAIN MOVLW b'00000001' ;RB0 in input, the rest are outputTRIS PORTBMOVLW b'10000000' ;interrupt occurs at falling edgeOPTIONCLRF PORTBBSF PORTB,7 ;Only LED PortB,7 is onBSF INTCON,INTE ;Interrupt RB0 enabledBSF INTCON,GIE ;All interrupts enabled

Interrupt on Pin RB0 cont…

LOOPGOTO LOOP ;Main Loop

ISR BCF INTCON,INTF ;Clear the flag that indicates RB interrupt;took place thus enabling detection of ;new interrupt in main program

BTFSS PORTB,7 ;Is LED 7 on?GOTO Lab1BCF PORTB,7 ;If true switch off LED7RETFIE

Lab1BSF PORTB,7 ;If false switch on LED7RETFIEEND

Hardware Counter/Timer

For accurate timing and counting Sensor on motor shaft pulse/resolution Shaft speed no of pulses / second Timer measures interval between pulse

calculate speed Process:-

1. Wait for pulse2. Read and reset the timer3. Restart the timer4. Process previous timer reading5. Go to 1

Using TMR0

PrescalerX X X X X X X X

X X X 0 0 0 0 0

TMR0 register

Load / readTMR0 register

TMR0 input

Prescalevalueselect

Inputselect

Edgeselect

RA4 CLKIN/4

PreScaleenable

1 X 1 X X 1 X XBit 7 6 5 4 3 2 1 0

INTCON register

2 T0IFTMR0 overflow interrupt flag

0 = No Overflow1 = Overflow

5 T0IETMR0 overflow interrupt enable

0 = Disable1 = Enable

7 GIEGlobal Interrupt enable


Bit Timer interrupt bit label and function

0 PS0 Prescaler rate select bit 0 0 1 0 1 0 1 0 11 PS1 Prescaler rate select bit 1 0 0 1 1 0 0 1 12 PS2 Prescaler rate select bit 2 0 0 0 0 1 1 1 1

3 PSA Prescaler assignment bit 0 = Select prescaler for TMR01 = Deselect prescaler for TMR0

4 T0SE TMR0 source edge select bit 0 = Increment on rising edge of RA41 = Increment on falling edge of RA4

5 T0CS TMR0 clock source select bit 0 = Instruction clock = Ext Clock/41 = Select RA4 input

Prescaler division ratio2 4 8 16 32 64 128 256

Bit 7 6 5 4 3 2 1 0

OPTION register

TMR0 overflow

Interrupt or poll

PrescalerX X X X X X X X

X X X 0 0 0 0 0

TMR0 register

Load / readTMR0 register

TMR0 input

Prescalevalueselect

Inputselect

Edgeselect

RA4 CLKIN/4

PreScaleenable

1 X 1 X X 1 X XBit 7 6 5 4 3 2 1 0

INTCON register

2 T0IFTMR0 overflow interrupt flag

0 = No Overflow1 = Overflow

5 T0IETMR0 overflow interrupt enable


7 GIEGlobal Interrupt enable


Bit Timer interrupt bit label and function

0 PS0 Prescaler rate select bit 0 0 1 0 1 0 1 0 11 PS1 Prescaler rate select bit 1 0 0 1 1 0 0 1 12 PS2 Prescaler rate select bit 2 0 0 0 0 1 1 1 1

3 PSA Prescaler assignment bit 0 = Select prescaler for TMR01 = Deselect prescaler for TMR0

4 T0SE TMR0 source edge select bit 0 = Increment on rising edge of RA41 = Increment on falling edge of RA4

5 T0CS TMR0 clock source select bit 0 = Instruction clock = Ext Clock/41 = Select RA4 input

Prescaler division ratio2 4 8 16 32 64 128 256

Bit 7 6 5 4 3 2 1 0

OPTION register

TMR0 overflow

Interrupt or poll

Counter Mode

Timer Mode

Set OPTION register to select internal clock (bit 5 = 0)

Crystal oscillator, 4MHz/4 1s TMR0

Example 7.2

Adjustable CR clock with freq. of 65536Hz

65536/(4x64=256)=256Hz

Timer counts from 0 256 & overflow every seconds

Need 256s to complete 8-bit binary o/p count

Freq division

prescalar

Example 7.3

Each example in the program takes four clock cycles to complete, with jumps taking eight cycles. If the program sequence is studied carefully, extra time is taken in completing the program loop before the timer is restarted. In this application, it will cause only a small error, but in other applications it may be significant.

Efficient solution: run timer while carrying on other process on the processor and allow time-out condition to interrupt the main program when it is finished.

Example 7.3 cont…

;Register Label Equates ......................................

TMR0 EQU 01 ;Counter/Timer RegisterPORTB EQU 06 ;Port B Data Register (LEDs)INTCON EQU 0B ;Interrupt Control Register

T0IF EQU 02 ;Timer Interrupt Flag

;*************************************************************

;Initialize Port B (Port A defaults to inputs)..........

MOVLW b'00000000'TRIS PORTB

MOVLW b'00000101' ;Set up Option registerOPTION ;For internal timer /64

CLRF PORTB ;Clear Port B (LEDs Off)

Example 7.3 cont…

;Main output loop.......................................

next CLRF TMR0 ;Clear timer registerBCF INTCON,T0IF ;Clear time-out flag

check BTFSS INTCON,T0IF ;Wait for next time-outGOTO check ;by polling time-out flag

INCF PORTB ;Increment LED CountGOTO next ;repeat

END

Interrupt by Overflow on TMR0

Interrupt by Overflow on TMR0 cont…

;PROGRAM INTTOCK.ASM

#include "P16F84.INC"

ORG 0x00GOTO MAINORG 0x04GOTO ISR

MAIN MOVLW 0x00TRIS PORTB ;Set port B as outputMOVLW 0xFFTRIS PORTA ;Set port A as inputMOVLW b'10100001‘ ;Setup OPTION registerOPTIONCLRF PORTBBSF INTCON,T0IE ;Enable TMR0 interruptBSF INTCON,GIE ;Interrupts are globally Enabled

Interrupt by Overflow on TMR0 cont…

LOOPGOTO LOOP

ISR BCF INTCON,T0IF ;Clear interrupt FlagINCF PORTBRETFIE

END

Serial Communication

SenderSender ReceiverReceiverSenderSender ReceiverReceiver

Serial Transfer

Parallel Transfer

D0

D7

Serial Communication cont…

Two methods of serial data communication: asynchronous & synchronous

Asynchronous serial communication:

104us (9600 baud)

RS232 Standard

Short distance: 15m data rates: 50 to 76800 baud (bits/s)

(Ring Indicator)9. RI

(Clear To Send)8. CTS

(Request To Send)7. RTS

(Data Set Ready)6. DSR

(Ground)5. GND

(Data terminal Ready)4. DTR

(Transmit Data)3. TXD

(Receive Data)2. RXD

(Carrier Detect)1. CD

(Ring Indicator)9. RI

(Clear To Send)8. CTS

(Request To Send)7. RTS

(Data Set Ready)6. DSR

(Ground)5. GND

(Data terminal Ready)4. DTR

(Transmit Data)3. TXD

(Receive Data)2. RXD

(Carrier Detect)1. CD

Pin designations on RS232 connector

Electrical Signal Characteristic

Negative logic & bipolar power supplies Letter ‘Q’ 51h(ASCII)

51h = 01010001b – transmitted as 1001010

-V

+V

Sta

rt b

it 1 0 0 0 1 0 1 0

Sto

p b

it

-V

+V

Sta

rt b

it 1 0 0 0 1 0 1 0

Sto

p b

it

Example 7.4

Given ‘J’ = 49h = 1001001 & ‘K’ = 4Ah = 1001010

‘J’ transmitted in 7-bit even parity : 10010011 ‘J’ transmitted in 7-bit odd parity : 10010010 ‘K’ transmitted in 7-bit even parity : 01010011 ‘K’ transmitted in 7-bit odd parity : 01010010 Baud rates: 75, 150, 300, 600, 1200, 2400, 4800 Data rate:

baud rate/(start bit + bit of data + stop bit)Example:300/(1 + 8 + 1) 30 bytes per second

Voltage Level Conversion

Two internal power supplies:

- Voltage doubler: raise the +5 V to +10 V

- Voltage inverter: convert +10 V to -10 V

Voltage Level Conversion cont…

Macro for serial communication

Analogue to Digital Conversion

Temperature measurement Sound a buzzer if the temperature drops below

freezing. Turn a heater on if the temperature is below 18C. Turn on a fan if the temperature goes above 25C. Turn on an alarm if the temperature goes above 30C

A/D reading 0°C gives a reading of 0V 18°C gives a reading of 1.4V 25°C gives a reading of 2.4V 30°C gives a reading of 3.6V

Analogue to Digital Conversion cont…

0V 0 & 5V 255 51 per volt @ resolution @ 1/51 V, i.e. 1

bit is 19.6 mV Therefore

0°C = 0.6V reading of 31 (0.6 x 51 = 30.6) 18C = 1.4v = 71 (1.4 x 51 = 71.4) 25°C = 2.4v = 122 (2.4 x 51 = 122.4) 30°C = 3.6\' = 184 (3.6 x 51 = 1836)


Device I/OA/D

ChannelsProgram Memory

Data Memory

Current Source/Sink

16C71 13 4 1k 36 25mA

16C73 22 5 4k 192 25mA

16C75 33 8 4k 192 25mA

16C710 13 4 512 36 25mA

16C711 13 4 1k 68 25mA

16C715 13 4 2k 128 25mA

16C72 22 5 2k 128 25mA

16C76 22 5 8k 368 25mA

16C77 33 8 8k 368 25mA

16C7X device specifications


Memory map of the 16C711


ADNADIFGOCHS0CHS1-ADCS0ADCS1Bit Name

01234567Bit no.

ADNADIFGOCHS0CHS1-ADCS0ADCS1Bit Name

01234567Bit no.

A/D clock select: Select how long the PIC takes over a A/D conversion00: Fosc/201: Fosc/810: Fosc/3211: FRC

A/D on bit:1: ADC is on0: ADC is off

A/D int. flag:1: A/D int. occurred0: no A/D int. occurred

GO/DONE:1: Conversion in progress, setting

this bit start conversion0: Conversion has finished

Channel select:00: RA0/AN001: RA1/AN110: RA2/AN211: RA3/AN3

Reserved

A/D on bit:1: ADC is on0: ADC is off

A/D int. flag:1: A/D int. occurred0: no A/D int. occurred

GO/DONE:1: Conversion in progress, setting

this bit start conversion0: Conversion has finished

Channel select:00: RA0/AN001: RA1/AN110: RA2/AN211: RA3/AN3

Reserved

ADCON0 file register


7 GIE Global 0 = Disabledinterrupt enable 1 = Enabled

6 ADIE A/D conversion 0 = Disabledinterrupt 1 = Enabled A/D interruptenable

5 T0IE RB0 0 = Disabledinterrupt enable 1 = Enabled

4 INTE TMR0 overflow 0 = Disabledinterrupt enable 1 = Enabled

3 RBIE Port B (4:7) 0 = Disabledinterrupt enable 1 = Enabled

2 T0IF TMR0 overflow 0 = No overflowinterrupt flag 1 = overflow detected

1 INTF RB0 0 = No interruptinterrupt flag 1 = Interrupt detected

0 RBIF Port B (4:7) 0 = No Changeinterrupt flag 1 = Bit change detected

INTCON

Bit Label Function Setting

7 GIE Global 0 = Disabledinterrupt enable 1 = Enabled

6 ADIE A/D conversion 0 = Disabledinterrupt 1 = Enabled A/D interruptenable

5 T0IE RB0 0 = Disabledinterrupt enable 1 = Enabled

4 INTE TMR0 overflow 0 = Disabledinterrupt enable 1 = Enabled

3 RBIE Port B (4:7) 0 = Disabledinterrupt enable 1 = Enabled

2 T0IF TMR0 overflow 0 = No overflowinterrupt flag 1 = overflow detected

1 INTF RB0 0 = No interruptinterrupt flag 1 = Interrupt detected

0 RBIF Port B (4:7) 0 = No Changeinterrupt flag 1 = Bit change detected

INTCON

Bit Label Function Setting

INTCON register for 16C711


BSF ADCON0,2 ;start A/D conversion

ADLOOP BTFSC ADCON0,2 ;has conversion finished?

GOTO ADLOOP ;no, so keep looking

.... ;yes, so exit loop

A/D clock source Device frequency

Operation ADC 1:0 20MHz 16MHz 4MHz 1MHz 333.3kHz

2Tosc 00 100ns 125ns 500ns 2.0µs 6µs

8Tosc 01 400ns 500ns 2.0µs 8.0µs 24µs

32Tosc 10 2.0µs 2.0µs 8.0µs 32µs 96µs

RC 11 2-6µs 2-6µs 2-6µs 2-6µs

Example

You have connected a 4 MHz oscillator to the PIC, and set the A/D clock cycle to Fosc/2. The frequency for the A/D clock is therefore 2 MHz (=4/2), and one cycle lasts 0.5 µs.

Note: 0.5 µs is too little time, something between

2 µs and 8 µs is recommended.

Example cont…

- - - - - - PCFG1 PCFG0- - - - - - PCFG1 PCFG0

Bit 7 Bit 0

A/D Port Configurationbits

Bit 1 Bit 0 RA0 RA1 RA2 RA3 Ref

0 0 A A A A VDD

0 1 A A A Vref RA3

1 0 A A D D VDD

1 1 D D D D VDD

Possible combination of ADCON1

Example 7.5

The following figure shows the circuit for a water temperature alarm system. The operations of the system are as follow:

If temperature is lower than 18C, then the water is too cold, so turn on the L1 LED (others off).

If temperature is higher than 23C, then the water is too hot, so turn on the L3 LED (others off).

If temperature is in between 18C and 23C, then the water temperature is OK, so turn on the L2 LED (others off).

Example 7.5 cont…

RA/AIN0RA/AIN1RA/AIN2RA/AIN3

RB0RB1RB2RB3RB4RB5RB6RB7

1718

12

6789

10111213

RTCCMCLR

OSC1OSC2/CLK

3

4

16

15

R410K

1

23

TEMPLM35

R610K

D11N1418

L1 L2 L3

R1270

R2270

R3270

PIC16C711

+5V

0V

R51K

C120pF

C21µF



1718

12

6789

10111213

RTCCMCLR

OSC1OSC2/CLK

3

4

16

15



1718

12

6789

10111213

RTCCMCLR

OSC1OSC2/CLK

3

4

16

15

R410K

1

23

TEMPLM35

R610K

D11N1418

L1 L2 L3

R1270

R2270

R3270

PIC16C711

+5V

0V

R51K

C120pF

C21µF

Example 7.5 cont…

Start

Setup

Start A/D conversion

Start

Setup

Start A/D conversion

Reset A/D interrupt flag

Is water too cold?

Is water too hot?

Turn on OK LED Turn on hot LED Turn on cold LED

Return from ISR

YES

YES

NO

NO

Reset A/D interrupt flag

Is water too cold?

Is water too hot?

Turn on OK LED Turn on hot LED Turn on cold LED

Return from ISR

YES

YES

NO

NO

Main loop

Interrupt Service Routine

Example 7.5 cont…

include "P16C71.INC"

ORG 0x00GOTO startORG 0x04GOTO ISR

start MOVLW b'00000001' ;RA0: temperature sensorTRIS PORTA ;RA1-4 is not connectedMOVLW 0x00 ;RB0-2 is outputTRIS PORTB ;RB3-7 is not connected

MOVLW b'00000000' ;TMRO prescaled at 256OPTION

MOVLW b'01000001' ;Sets up A/D registerMOVWF ADCON0 ;Fosc/8, AN0, converter is on

MOVLW b'11000000' ;Sets up interrupt registerMOVWF INTCON

Example 7.5 cont…

main BSF ADCON0,2 ;Start A/D conversionGOTO main

ISR BCF ADCON0,1 ;Reset A/D interrupt flagMOVLW d'18' ;Compares result with the decimalSUBWF ADRES,W ;number 18 without affecting ADRESBTFSS STATUS,CGOTO cold ;less than 18, so too cold

MOVLW d'23' ;Compares result with the decimalSUBWF ADRES,W ;number 23 without affecting ADRESBTFSS STATUS,CGOTO OK ;less than 23, so OKGOTO hot ;more than 23, so hot

Example 7.5 cont…

cold MOVLW b'00000001' ;Turns on cold LED (others off)MOVWF PORTBRETFIE

OK MOVLW b'00000010' ;Turns on OK LED (others off)MOVWF PORTBRETFIE

hot MOVLW b'00000100' ;Turns on hot LED (others off)MOVWF PORTBRETFIE

END

Chp7 pic 16 f84 interfacing - copy

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