PIC Microcontroller and E b dd d S tEmbedded...

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 1-1

Chapter 2:pPIC Architecture And A bl L Assembly Language Programming Programming.

The WREG Register

PIC Microcontroller d E b dd d S

The PIC File RegisterUsing instruction with the default

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

access bank

Danny Causey, February 2007.

The PIC uCs 1-2

OutlineOutline

P PIC Status RegisterPIC data format and directiveIntro. To PIC assembly languageAssembling and linking a PIC programAssembling and linking a PIC programThe Program Counter and program ROM space in the PICspace in the PICRISC Architecture in the PICViewing Register and memory with MPLAB simulator

The PIC uCs 1-3

ObjectiveObjective

E h d f l f h P Examine the data RAM fileReg of the PIC uCManipulate data using the WREG & MOVEp gPerform simple operations such ADD and fileReg using and access bank in the PIC uCfileReg using and access bank in the PIC uCExplain the purpose of the status regDiscuss data RAM memory space allocation in Discuss data RAM memory space allocation in the PIC uCLi SFR f h PIC CList SFRs of the PIC uCDescribe PIC data types and directives

The PIC uCs 1-4

The WREG RegisterThe WREG Register

M i f i h i d l i Many registers for arithmetic and logic operation.The WREG (WORking Register) Register is one of the most widely used registers of y gthe PIC

8-bit register any data larger than 8 bits g y gmust be broken into 8-bits chunks before it is processed.There is only one .D7 D6 D5 D2D4 D3 D1 D0

The PIC uCs 3-5

MOVLWMOVLW

b d EGMoves 8-bit data into WREGMOVLW k; move literal value k into WREG

ExampleMOVLW 25HMOVLW A5H

Is the following code correct?MOVLW 9HMOVLW 9HMOVLW A23H

The PIC uCs 1-6

ADDLWADDLW

DDLW k dd li l l k WREG (k WREG)ADDLW k; Add literal value k to WREG (k +WREG)

0 0 0 01 0 1 0Example:MOVLW 12H ;ADDLW 16H ;

0 0 0 01 0 1 0

0 0 1 00 1 0 0ADDLW 16H ;ADDKW 11H ;ADDLW 43H ;

0 0 1 00 1 0 0

0 0 1 01 1 0 1ADDLW 43H ; 0 0 1 01 1 0 1

0 1 1 11 1 0 00 1 1 11 1 0 0

The PIC uCs 1-7

Figure 2-1. PIC WREG and ALU Using Literal Value

The PIC uCs 1-8

The PIC File RegisterThe PIC File Register

h d It is the data memory.Read/Write Static RAMUsed for data storage, scratch pad and registers for internal use and function8-bit width

PIC File Register

General Purpose RAM

Special Function Registers

GP RAM EEPROM

The PIC uCs 1-9

Register File ConceptRegister File ConceptRegister File Concept: All of data

Data Memory(Register File)

Concept: All of data memory is part of the register file, so any location in data

w fALU

07h

08h

09h

Dat

a B

us

d

any location in data memory may be operated on directly

w f

0Ah

0Bh

0Ch

D directlyAll peripherals are mapped into data

0Dh

0Eh

0Fh

10h memory as a series of registersOrthogonal

WREG10h

Decoded Instruction from Program Memory:

gInstruction Set: ALL instructions can operate on ANY

Opcode d a Address

The PIC uCsThe PIC uCs

Arithmetic/Logic Function to be Performed Result

Destination

Address of Second Source Operand

pdata memory location 1-10

PIC18F Programming ModelPIC18F Programming Model

The PIC uCs 1-11

Special Function RegistersSpecial Function Registers

d d d f f h dedicated to specific functions such as ALU status, timers, serial communication, / DI/O ports, ADC,…

The function of each SFR is fixed by the yCPU designer at the time of design

it is used for control of the microcontroller or peripheral

8-bit registersgTheir numbers varies from one chip to another

The PIC uCs

another.1-12

General Purpose RAMGeneral Purpose RAM

G f lGroup of RAM locations8-bit registersgLarger than SFR

Difficult to manage them by using Assembly Difficult to manage them by using Assembly languageEasier to handle them by C Compiler.y p

The microchip website provides the data The microchip website provides the data RAM size, which is the same as GPR size.

The PIC uCs 1-13

File Register Size File Register Size

File Register=

SFR+

GPR= +

(Bytes) (Bytes) (Bytes)PIC12F508 32 7 25PIC12F508 32 7 25PIC16F84 80 12 68PIC18F1220 512 256 256PIC18F1220 512 256 256PIC18F452 1792 256 1536PIC18F2220 768 256 512PIC18F458 1792 256 1536PIC18F8722 4096 158 3938

The PIC uCsPIC18F4550 2048 160 1888

1-14

Figure 2-2. File Registers of PIC12, PIC16, and PIC18

The PIC uCs 1-15

The PIC uCs 1-16

GPRAM VS EEPROMGPRAM VS. EEPROM

dd An add-on memoryCan be zero size

The PIC uCs 1-17

File Register and access bank in the PIC18

h P 1 F l h f 40 6 The PIC18 Family can have a max. of 4096 Bytes.The File Register

has addresses of 000- FFFHdivided into 256-byte banksMax. 16 banks (How?)( )

At least there is one bankKnown as default access bankKnown as default access bank.

Bank switching is a method used to access all the banks

The PIC uCs

all the banks1-18

Figure 2-3. File Register for PIC18 Family

The PIC uCs 1-19

Access bank in the PIC18Access bank in the PIC18

6 B b kIt is 256-Byte bank.Divided into equal two discontinuous qsections (each 128 B).

GP RAM, from 0 to 7FHSFR, from F80H to FFFH

The PIC uCs 1-20

Figure 2-4. SFRs of the PIC18 Family.

The PIC uCs 1-21

Using instruction with the default access bank

d h We need instruction to access other locations in the file register for ALU and

h other operations.MOVWFCOMFDECFMOVFMOVFF

The PIC uCs 1-22

MOVWF instructionMOVWF instruction

F d f f l F indicates for a file registerMOVWF Address

It tells the CPU to copy the source register, WREG, to a destination in the file register, WREG, to a destination in the file register.

A location in the SPRA location in the SPRA location in GP RAM

WREG

The PIC uCs 1-23

Example 2-1Example 2-1

MOVLW 99H 99 Add D t

WRFG

MOVLW 99H MOVWF 12H

99 Address Data012H013H85MOVLW 85H

MOVWF 13H014H015H016H3F

85

MOVLW 3FH MOVWF 14H

016H3FAddress Data

MOVLW 63H MOVWF 15H

63 012H 99013H 85014H 3F

MOVLW 12H MOVWF 16H

12014H 3F015H 63016H 12

The PIC uCs 1-24

NoteNote

l l l d l We cannot move literal values directly into the general purpose RAM location in the P 18 h b d h PIC18. They must be moved there via WREG.

The PIC uCs 1-25

ADDWFADDWF

dd h h f EG d Adds together the content of WREG and a file register location

ADDWF File Reg. Address, DThe result will be placed in either the The result will be placed in either the WREG or in the file register location

D indicates the destination bitD indicates the destination bitIf D=0 or (D=w)

The result will be placed in the WREGThe result will be placed in the WREGIf D=1 or (D=f)

Th l ill b l d i h fil iThe PIC uCs

The result will be placed in the file register1-26


h f f l l State the content of file register location and WREG after the following program

MOVLW 0 MOVWF 12H 0 Address Data

012H 0

Address Data012H 22Address Data012H 44Address Data012H 66

Address Data012H 88MOVWF 12H

MOVLW 22H ADDWF 12H F

012H 0013H014H

22 013H014H015H

012H 44013H014H

012H 66013H014H013H014H015HADDWF 12H, F

ADDWF 12H, F015H016H

015H016H015H016H015H016H015H016H

ADDWF 12H, FADDWF 12H, F

The PIC uCs

DDWF H, F

1-27


h f f l l State the content of file register location and WREG after the following program

MOVLW 0 MOVWF 12H 0 Address Data

012H 0Address Data012H 22MOVWF 12H

MOVLW 22H ADDWF 12H F

013H014H015H

22012H 22013H014H

ADDWF 12H, FADDWF 12H, W

015H016H015H016H44

ADDWF 12H, WADDWF 12H, W

6688

The PIC uCs

DDWF H, W

1-28

88

Figure 2-5. WREG, fileReg, and ALU in PIC18

The PIC uCs 1-29

COMF instructionCOMF instruction

F F l dd DCOMF File Reg. Address, DIt tells the CPU to complement the content pof fileReg and places the results in WREG or in fileReg.g

The PIC uCs 1-30


l l h F Write a simple program to toggle the SFR of Port B continuously forever.

SolutionMOVLW 55H

55 Address DataF81H 55HAddress Data

MOVLW 55HMOVWF PORTB

B1 F P B F

F81H 55HF82HF83H

F81H AAHF82HF83H

B1 COMF PORTB, FGOTO B1

F83H

The PIC uCs 1-31

DECF instructionDECF instruction

DE F F l dd DDECF File Reg. Address, DIt tells the CPU to decrement the content of fileReg and places the results in WREG or in fileReg.

3 Address DataAddress Datag

Example:MOVLW 3

3 Address Data012H 3013H

Address Data012H 2013HMOVLW 3

MOVWF 20HDECF 20H F

014H015H016H

014H015H016HDECF 20H, F

DECF 20H, FDECF 20H F

016H016H

The PIC uCs

DECF 20H, F

1-32

DECF instructionDECF instruction

DE F F l dd DDECF File Reg. Address, DIt tells the CPU to decrement the content of fileReg and places the results in WREG or in fileReg.

3 Address DatagExample:

MOVLW 3

3 Address Data012H 3013H2MOVLW 3

MOVWF 20HDECF 20H w

014H015H016H

1DECF 20H, wDECF 20H, wDECF 20H w

016H

0

The PIC uCs

DECF 20H, w

1-33

MOVF instructionMOVF instruction

F F l dd DMOVF File Reg. Address, DIt is intended to perform MOVFWp

MOVFW isn’t existedIf D=0If D 0

Copies the content of fileReg (from I/O pin) to WREG

If D=1The content of the fileReg is copied to itself The content of the fileReg is copied to itself. (why?)

The PIC uCs 1-34

MOVF instructionMOVF instruction

F F l dd 0MOVF File Reg. Address, 0

WREG

The PIC uCs 1-35


l d f Write a simple program to get data from the SFRs of Port B and send it the SFRs of P R lPORT C continuously.

Solution XX Address DataF81H XX

Address DataF81H XX

AGAIN MOVF PORTB, WMOVWF PORTC

F81H XXF82HF83H

F81H XXF82H XXF83HMOVWF PORTC

GOTO AGAIN

The PIC uCs 1-36


l d f Write a simple program to get data from the SFRs of Port B Add the value 5 to it

d d h FR f P R and send it the SFRs of PORT C Solution 55

Address DataF81H 55H

Address DataF81H 55H5A

MOVF PORTB,WADDLW 05H

55 F81H 55HF82HF83H

F81H 55HF82H 5AHF83H

5A

ADDLW 05HMOVWF PORTC

The PIC uCs 1-37

MOVFF instructionMOVFF instruction

d f l F lIt copies data from one location in FileRegto another location in FileReg.

MOVFF Source FileReg, destination FileReg

The PIC uCs 1-38


l d f Write a simple program to get data from the SFRs of Port B and send it the SFRs of P R lPORT C continuously.

Solution XX Address DataF81H XXAddress DataF81H XX

AGAIN MOVFF PORTB, PORTCGOTO AGAIN

F81H XXF82HF83H

F81H XXF82H XXF83H

GOTO AGAIN

The PIC uCs 1-39

PIC Status RegisterPIC Status Register

d h d To indicate arithmetic conditions It is a 8-bit registerg

Five bits are usedD0: C Carry FlagD0 C Carry FlagD1: DC Digital Carry FlagD2: Z Z FlD2: Z Zero FlagD3: OV Overflow FlagD4: N Negative Flag

The PIC uCs 1-40

Figure 2-7 Bits of Status RegisterFigure 2 7. Bits of Status Register

The PIC uCs 1-41


h h f h D fl f Show the status of the C, DC, Z flags after the following addition instruction

MOVLW 38HADDLW 2FHADDLW 2FH

Solution38H + 2FH 67H WREG 67H38H + 2FH = 67H WREG=67H

C=0DC 1DC=1Z=0

The PIC uCs 1-42


h h f h D fl Show the status of the C, DC, Z flags after the following addition instruction

MOVLW 9CHADDLW 64HADDLW 64H

Solution9CH + 64H 100H WREG 00H9CH + 64H = 100H WREG= 00H

C=1DC 1DC=1Z=1

The PIC uCs 1-43

Instruction That Affect Flag Bits

The PIC uCs 1-44


The PIC uCs 1-45


The PIC uCs 1-46

Flag Bits and Decision MakingFlag Bits and Decision Making

The PIC uCs 1-47

PIC Data Format and DirectivesPIC Data Format and Directives

h d There is one data type8 bitsIt is the job of the programmer to break down data larger 8 bits

Data type can be positive or negativeData format are

Hex (default in PIC) 12 or 0x12 or H'12' or 12HBinary B'00010010' B nary B 000 00 0 Decimal .12 or D'12' ASCII A'c' or a'c'

The PIC uCs

ASCII A c or a c

1-48

Assembler Directives Assembler Directives

h h d ff b What is the difference between Instruction and Directives?EQU

Defines a constant or fixed addressSET

Defines a constant or fixed addressDefines a constant or fixed addressMaybe reassigned later

ORG (Origin)ORG (Origin)END

The PIC uCsLIST

1-49

Rules for labels in A LRules for labels in A.L.

Unique nameAlphabetic lettersp

Upper, lower, digits (0-9),special char. (? . @_ $)

The first letter must be Alphabetic lettersNot a reserved wordNot a reserved word

The PIC uCs 1-50

Introduction to PIC Assembly Language

D ff l f d l h h h Difficult for us to deal with the machine code ( 0s and 1s)Assembly Language provide

Mnemonic: codes and abbreviations that are easy to remember Faster programming and less prone errorLLL (why?)Programmer must know all Reg. …etc.

Assembler is used to translate the assembly code into machine code (object

The PIC uCs

m y m ( jcode)

1-51

Structure of Assembly Language

f lSeries of linesInstructionDirectives

Consists of four field[label] mnemonic [operands] [;commands]

Label: refer to line by code (certain length)Label: refer to line by code (certain length)Mnemonic and operands are task that sh ld b t dshould be executed.

Directive don’t generate any machine code and used by assembler

The PIC uCs

used by assembler 1-52

Sample of Assembly Language Program

UM EQU 10H R M l 10H f UMSUM EQU 10H ;RAM loc 10H fro SUMORG 0H; start at address 0MOVLW 25H ; WREG = 25ADDLW 0x34 ;add 34H to WREG=59HADDLW 11H ;add 11H to WREG=6AHADDLW D’18’ ; W = W+12H=7CHADDLW 1CH ; W = W+1CH=98HADDLW b’00000110’ ; W = W+6H=9EHMOVWF SUM ;save the result in SUM location

HERE GOTO HERE ;stay here forever

The PIC uCsEND ; end of asm source file

1-53

Assembling and Linking A PIC Program

Figure 2Figure 2-8. Steps

C to Create a Programg

The PIC uCs 1-54

List FileList File

The PIC uCs 1-55

The Program Counter and Program ROM Space in the PIC

P (P ) d b h P Program Counter (PC) is used by the CPU to point to the address of the next

b dinstruction to be executedThe wider the program counter, more the p gmemory locations can be accessed

PIC16 has 14 bits (8K)( )PIC18 has 21 bits (2M)8051 has 16 bits (64K)( )

The PIC uCs 1-56

Figure 2-9. Program Counter in PIC18

The PIC uCs 1-57

The PIC uCs 3-58

Example 2-11Example 2 11

F d h dd f h f Find the ROM Memory Address of each of the following PIC chips:

a) PIC18F2220b) PIC18F2410b) PIC18F2410c) PIC18F458

The PIC uCs 1-59

P i UPAt what address does the

Powering UPAt what address does the CPU wake up when power applied?applied?• The uC wakes up at

mem r address 0000memory address 0000• The PC has the value 0000• ORG directive put the

address of the first op pcode at the memory location 0000

The PIC uCs 1-60

Figure 2-11. PIC18 Program ROM Space

Placing Code in program ROMPlacing Code in program ROM

The PIC uCs 1-61

Program MemoryProgram Memory

All instructions are 2Byte All instructions are 2Byte except the GOTO, which has 4-Byte

The PIC uCs 1-62

Program ROM Width for the PIC18

B dd bl h l h ld l Byte addressable: each location holds only one byte

CPU with 8-Bit will fetch one byte a timeIncreasing the data bus will bring more information

Solution: Data bus between CPU and ROM can be similar to traffic lanes on the highwayg yThe wide of Data path is 16 bit

Increase the processing powerIncrease the processing powerMatch the PIC18 instruction single

cycle

The PIC uCs

cycle

1-63

Figure 2-12. Program ROM Width for the PIC18

The PIC uCs 1-64

Little endian VS big endian warLittle endian VS big endian war

h l b h l The low byte goes to the low memory locationThe high byte goes to the high memory locationIntel uP and many uCs use little endian

The PIC uCs 1-65

Figure 2-13. PIC18 Program ROM Contents for Program 2-1 List File

The PIC uCs 1-66

Harvard Architecture in the PIC

N h h Von Neumann Architecture: uses the same bus for accessing both the code and data memory.

Slow down the processing speedGet in each other’s way

Harvard Architecture: uses separate buses pfor accessing the code and data memory.

Inexpensive for a chipp p

The PIC uCs 1-67

Figure 2-14. von Neumann vs. Harvard Architecture

The PIC uCs 1-68

Instruction size of the PIC18Instruction size of the PIC18

P B 4 BPIC Instructions are 2-Byte or 4-ByteThe first seven or eight bits represents g pthe op-codeMost of PIC18 instructions are 2-ByteMost of PIC18 instructions are 2 Byte

MOVLW 0000 1110 kkkk kkkk (0E XX)ADDLW 0000 1111 kkkk kkkk (0F XX)ADDLW 0000 1111 kkkk kkkk (0F XX)MOVWF 0110 111a ffff ffff (6E XX

or 6F XX)F )• A specifies the default access bank if it is 0 and if a

= 1 we have to use bank switching

The PIC uCs 1-69

Instruction size of the PIC18Instruction size of the PIC18

4 B l d 4-Byte instructions include MOVFF (move data within RAM, which is 4k)

• 1100 ssss ssss ssss (0≤ fs ≤ FFF)• 1111 dddd dddd dddd (0≤ fd ≤ FFF)

GOTO (th d dd b idth i 21 hi h GOTO (the code address bus width is 21, which is 2M)

• 1110 1111 k kkk kkkk01110 1111 k7kkk kkkk0

• 1111 k19kkk kkkk kkkk8

The PIC uCs 1-70

RISC Architecture in the PICRISC Architecture in the PIC

h f h To increase the processing power of the CPU1. Increase the clock frequency of the chip2. Use Harvard architecture 3. change the internal architecture of the CPU

and use what is called RISC architecture

The PIC uCs 1-71


RISCSimple and Small

CISCComplex and large p

instruction setRegular and fixed

p ginstruction setIrregular instruction Regular and fixed

instruction formatSimple address

Irregular instruction formatComplex address Simple address

modesPipelined instruction

Complex address modesMay also pipeline Pipelined instruction

execution --> 95% executed in one cycle

May also pipeline instruction execution

The PIC uCs

executed in one cycle 1-72


RISCProvide large number

CISCProvide smaller number g

of CPU registersSeparated data and

of CPU registersCombined data and Separated data and

program memoryMost operations are

Combined data and program memoryMost operations can be Most operations are

register to registerTake shorter time to

Most operations can be register to memoryTake longer time to Take shorter time to

design and debugTake longer time to design and debug

The PIC uCs 1-73

Viewing Register and memory with MPLAB Simulater

The PIC uCs 1-74

Figure 2-15. SFR Window in MPLAB Simulator

The PIC uCs 1-75

Figure 2-16. File Register (Data RAM) Window in MPLAB Simulator

The PIC uCs 1-76

Figure 2-17. Program (Code) ROM Window in MPLAB ROM Window in MPLAB Simulator

The PIC uCs 1-77

Chapter 2: SummaryChapter 2: SummarySample PIC18 Sample PIC18 Instructions

Move add subtractMove, add, subtract

Next:Branch, Call and Time ,

Delay Loo

The PIC uCs 3-78

PIC Microcontroller and E b dd d S tEmbedded...

Documents

Transcript of PIC Microcontroller and E b dd d S tEmbedded...