PIC Microcontroller and E b dd d S tEmbedded Systems

Muhammad Ali Mazidi, Rolin McKinlay and Danny Causey

Eng. Husam AlzaqE g m qThe Islamic Uni. Of Gaza

The PIC uCs 4-1

Chapter 4:Chapter 4:PIC I/O Port /O ort Programming

I/O Port Programming in P

PIC Microcontroller d E b dd d S

PIC18I/O Bit Manipulation

and Embedded SystemsMuhammad Ali Mazidi, Rolin McKinlay and D C s F b

pProgramming

Danny Causey, February 2007.

The PIC uCs 4-2

ObjectiveObjective

ll h f h P 1List all the ports of the PIC18Describe the dual role of PIC18 pinspCode Assembly to use ports for input or outputoutputCode PIC instructions for I/O handling Code I/O bit manipulation Programs for Code I/O bit-manipulation Programs for PICE l i h bi dd bili f PIC Explain the bit addressability of PIC ports

The PIC uCs 4-3

I/O Port Programming in PIC18I/O Port Programming in PIC18

P 1 h PIC18 has many ports Depending on the family memberDepending on the number of pins on the chipEach port can be configured as input or output.

• Bidirectional portEach port has some other functions

• Such as timer , ADC, interrupts and serial communication

Some ports have 8 bits while others have notSome ports have 8 bits, while others have not

The PIC uCs 4-4

Figure 4-1. PICF458 Pin Diagram

The PIC uCs

Pins Add 18-pin 28-pin 40-pin 64-pin 80-pinp p p p pChip PIC18F1220 PIC18F2220 PIC18F458 PIC18F6525 PIC18F8525PORT A F80H X X X X XPORT B F81H X X X X XPORT C F82H X X X XPORT D F83H X X XPORT D F83H X X XPORT E F84H X X XPORT F F85H X XPORT F F85H X XPORT G F86H X XPORT H X XPORT J X XPORT K XPORT L X

The PIC uCs 4-6

I/O SFR I/O SFR

E h h h f Each port has three registers for its operation:

TRIS register (Data Direction register)• If the corresponding bit is 0 Output

If h di bi i 1 I• If the corresponding bit is 1 InputPORT register (reads the levels on the pins of the device)the device)LAT register (output latch)

Th D t L t h (LAT) ist is s f l The Data Latch (LAT) register is useful for read-modify-write operations on the

l th t th I/O pins d i inThe PIC uCs

value that the I/O pins are driving.4-7

I/O SFR Pins AddressPORT A F80HI/O SFR PORT A F80HPORT B F81HPORT C F82H

P 1 F4 h PORT C F82HPORT D F83HPORT E F84H

PIC18F458 has 5 ports

LATA F89HLATB F8AHLATC F8BH

Upon reset, all ports are

LATC F8BHLATD F8CHLATE F8DH

pconfigured as inputTRISx register LATE F8DH

TRISA F92HTRISB F93H

TRISx register has 0FFH

TRISC F94HTRISD F95H

The PIC uCs

TRISE F96H4-8

Figure 4-2. CMOS States for P and N Transistors

The PIC uCs

Figure 4-3. Outputting (Writing) 0 to a Pin in the PIC18

The PIC uCs

Figure 4-4. Outputting (Writing) 1 to a Pin in the PIC18

The PIC uCs

Figure 4-5. Inputting (Reading) 0 from a Pin in the PIC18

The PIC uCs

Figure 4-6. Inputting (Reading) 1 from a Pin in the PIC18

The PIC uCs

Port APort A

P b d b d l PORTA is a 7-bit wide, bidirectional port. Sometimes A6 is not available. why?

The corresponding Data Direction register is TRISA. Setting a TRISA bit (= 1) will make the corresponding PORTA pin an input corresponding PORTA pin an input Clearing a TRISA bit (= 0) will make the corresponding PORTA pin an output corresponding PORTA pin an output On a Power-on Reset, these pins are configured as inputs and read as ‘0’

The PIC uCs

configured as inputs and read as 0 .4-14

Example 1Example 1

MOVLW B’00000000’MOVLW B’00000000’MOVWF TRISA

B CK MOVLW 0 55

BACK MOVLW 0x55MOVWF PORTA

BACK MOVLW 0x55MOVWF PORTACALL DELAY

CALL DELAYMOVLW 0xAA

CALL DELAYMOVLW 0xAAMOVWF PORTA

MOVWF PORTACALL DELAY

MOVWF PORTACALL DELAYGOTO BACK

GOTO BACK

GOTO BACK

The PIC uCs 4-15

Example 2Example 2

MYREG EQU 0 20MYREG EQU 0x20MOVLW B’11111111’MOVWF TRISAMOVWF TRISAMOVF PORTA, w

F EG MOVWF MYREG

The PIC uCs 4-16

PORT B, PORT C, PORT D and PORT E

P B PORTB is 8 pinsPORTC is 8 pinspPORTD is 8 pinsPORTE is 3 pinsPORTE is 3 pins

The PIC uCs 4-17

Read followed by write operationRead followed by write operation

B f l F BBe carefulDon’t have a two I/O

h

CLRF TRISBSETF TRISC

operations one right after the other.

D t D d

L4 MOVF PORTC,WMOVWF PORTBData Dependency

A NOP is needed to k th t d t i

MOVWF PORTBBRA L4

make that data is written into WREG before it read for before it read for outputting to PortB.

The PIC uCs 4-18

Figure 4-7. Pipeline for Read Followed by Write I/O

The PIC uCs

Two SolutionsTwo Solutions

Solution1 Solution2Solution1 Solution2

CLRF TRISBSETF TRISC

CLRF TRISBSETF TRISCSETF TRISC

L4 MOVF PORTC,WSETF TRISCL4 MOVFF PORTC, PORTB

NOPMOVWF PORTB

BRA L4

BRA L4 MOVFF is 4-byte instruction

The PIC uCsThe PIC uCs

instruction.4-20

Example 4-1 list P=PIC18F458Example 4-1

W it t t

#include P18F458.INCR1 equ 0x07Write a test program

for the PIC18 chipt t l ll th

R1 equ 0x07R2 equ 0x08ORG 0to toggle all the

bits of PORTB,PORTC d PORTD

ORG 0CLRF TRISB

PORTC and PORTDevery 0.25 of a

d (

CLRF TRISCCLRF TRISDsecond. (suppose

that there is a 4MH )

CLRF TRISDMOVLW 0x55MOVWF PORTBMHz) MOVWF PORTBMOVWF PORTC

The PIC uCsMOVWF PORTD

4-21

SolutionQDELAY

MOVLW D'200'Solution MOVLW D 200MOVWF R1

D1 MOVLW D'250'L3 COMF PORTB,F

COMF PORTC F

D1 MOVLW D'250'MOVWF R2

COMF PORTC,FCOMF PORTD,F

D2 NOPNOP

CALL QDELAYBRA L3

NOPDECF R2, FBNZ D2BNZ D2DECF R1, FBNZ D1RETURN

The PIC uCs

RETURNEND 4-22

I/O Bit Manipulation ProgrammingI/O Bit Manipulation ProgrammingI/O ports and bit-addressabilityp yMonitoring a single bitR di i l biReading a single bit

Section 4-2The PIC uCs 3-23

I/O ports and bit-addressability

PORT A PORT B PORT C PORT D PORT E PORT BitRA0 RB0 RC0 RD0 RE0 D0RA0 RB0 RC0 RD0 RE0 D0RA1 RB1 RC1 RD1 RE1 D1RA2 RB2 RC2 RD2 RE2 D2RA2 RB2 RC2 RD2 RE2 D2RA3 RB3 RC3 RD3 D3RA4 RB4 RC4 RD4 D4RA5 RB5 RC5 RD5 D5

RB6 RC6 RD6 D6RB7 RC7 RD7 D7

The PIC uCs 4-24

Bit Oriented Instruction for PIC18

Instruction Function

BSF fileReg bit Bit Set File RegisterBSF fileReg, bit Bit Set File RegisterBCF fileReg, bit Bit Clear File Registerg, gBTG fileReg, bit Bit Toggl File Register

i il i ki ifBTFSC fileReg, bit

Bit Test File Register, skip if clear

BTFSS fileReg, bitBit Test File Register, skip if set

The PIC uCs

BTFSS fileReg, bit set4-25

Example 4-2 CLRFTRISDExample 4-2

ED d

BSF PORTD,0CALLDELAY

A LED is connected to each pin of port D

BSF PORTD,1CALLDELAYD. Write a program

to turn on each LED f D0

CALLDELAYBSF PORTD,2

LED from pin D0 to D4.

CALLDELAYBSF PORTD,3CALLDELAYBSF PORTD 4BSF PORTD,4CALLDELAY

The PIC uCs 4-26

Example 4-3 Solution 1Example 4-3

h f ll BCF TRISC 0 Write the following programs

BCF TRISC,0 HERE

BSF PORTC 0A. Create a square wave of 50% duty

BSF PORTC,0CALL DELAYy

cycle on bit 0 of C BCF PORTC,0CALL DELAYCALL DELAYBRA HERE

How many byte are d

The PIC uCs

used? 4-27

Example 4-3 Solution 2

h f ll Write the following programs BCF TRISC,0

BACK A. Create a square wave of 50% duty

BACK BTF PORTC,0y

cycle on bit 0 of C CALL DELAYBRA BACKBRA BACK

H m b t How many byte are used?

The PIC uCs 4-28

Example 4-4 BSF TRISB,2Example 4-4

F ,CLRF TRISCBCF PORTD 3Write a program to

perform the following:BCF PORTD,3MOVLW 0x45

a) Keep monitoring the RB2 bit until it

AGAINBTFSS PORTB,2

becomes HIGH (1)b) When RB2 becomes

,BRA AGAINMOVWF PORTCb) When RB2 becomes

HIGH, write value 45H to portC and

MOVWF PORTCBSF PORTD,345H to portC and

send a HIGH to LOW plus to RD3

CALL DELAYBCF PORTD,3

The PIC uCs

plus to D3 ,

4-29

Example 4-5Example 4-5

B B d Bit RB3 is an input and represents the

d f d condition of a door alarm.Whenever it goes LOW, send a HIGH-to-LOW pulse to RC5 to turn on a buzzer

The PIC uCs 4-30

SolutionSolution

B F BBSF TRISB,3BCF TRISC,5

HEREBTFSC PORTB 3BTFSC PORTB,3BRA HEREB F PORTC 5BSF PORTC,5BCF PORTC,5CALL DELAYBRA HERE

The PIC uCs

BRA HERE4-31

Reading a single bitExamole4-8

h BSF TRISB,0

A switch is connected to pin RB0 d LED

BCF TRISB,7 AGAIN

RB0 and a LED to pin RB7. Write a

d

G NBTFSS PORTB,0 GOTO OVERprogram to read

the status of SW d d i h

GOTO OVERBSF PORTB,7

and send it to the LED

GOTO AGAINOVERBCF PORTB,7 GOTO AGAIN

The PIC uCs

GOTO AGAIN4-32

Reading input pins VS. LATx port

h b l d ’ There are two possibilites to read port’s value

Through reading the status of the input pinThrough reading the internal latch of the LAT register.

• Some instructions do thatThe action is • The action is

1. The instruction read the latch instead of the pin2. Execute the instruction. Execute the nstruct on3. Write back the result to the Latch4. The data on the pins are changed only if the TRISx

bi l d

The PIC uCs

bits are cleared.

٣٣- ٤

FunctionInstruction Function InstructionAdd WREG from ffileReg,dADDWFBit S t fil Rfil R bitBSF Bit Set fileRegfileReg,bitBSFBit Clear fileRegfileReg,bitBCFComplement ffileReg,dCOMFIncrement FfileReg,dINCF gSubtruct WREG from ffileReg,dSUBWFExclusive-OR WREG with ffileReg,dXORWF

The PIC uCs

Exclusive OR WREG with ffileReg,dXORWF

٣٤- ٤

Figure 4-8. LATx Register Role in Reading a Port or Latch

The PIC uCs

Chapter 4: SummaryChapter 4: SummaryWe focused on the We focused on the I/O Ports of the PIC. These ports used for These ports used for input or output. ProgrammingProgrammingWe discussed Bit m nip l ti n

Next:Arithmetic, logic manipulation

instructions

, gInstruction and programs

The PIC uCs 4-36