PIC 16F84A programming (II)

Transcription

1 Lecture (05) PIC 16F84A programming (II) Dr. Ahmed M. ElShafee ١ Introduction to 16F84 ٣ PIC16F84 belongs to a class of 8-bit microcontrollers of RISC architecture. Program memory (FLASH) EEPROM RAM PORTA and PORTB FREE-RUN TIMER CENTRAL PROCESSING UNIT Agenda Introduction to 16F84 Assembly programming Examples ٢ PIC16F84 has a RISC architecture, or Harvard architecture in another word ٤

2 Instructions set 16F84 precisely 35 instructions. (ex. Intel's and Motorola's microcontrollers have over hundred instructions) All of these instructions are executed in one cycle except for jump and branch instructions. PIC16F84 usually reaches results of 2:1 in code compression and 4:1 in speed in relation to other 8-bit microcontrollers in its class. ٥ Pin no.7 RB1 First pin on port B. No additional function. Pin no.8 RB2 Second pin on port B. No additional function. Pin no.9 RB3 Third pin on port B. No additional function. Pin no.10 RB4 Fourth pin on port B. No additional function. Pin no.11 RB5 Fifth pin on port B. No additional function. Pin no.12 RB6 Sixth pin on port B. 'Clock' line in program mode. Pin no.13 RB7 Seventh pin on port B. 'Data' line in program mode. Pin no.14 Vdd Positive power supply pole. Pin no.15 OSC2 Pin assigned for connecting with an oscillator Pin no.16 OSC1 Pin assigned for connecting with an oscillator Pin no.17 RA2 Second pin on port A. No additional function Pin no.18 RA1 First pin on port A. No additional function. ٧ Pin description PIC16F84 has a total of 18 pins (DIP18 ) (Dual In Package) or (SMD 18) (Surface Mount Devices). Pin no.1 RA2 Second pin on port A. Has no additional function Pin no.2 RA3 Third pin on port A. Has no additional function. Pin no.3 RA4 Fourth pin on port A. TOCK1 which functions as a timer is also found on this pin Pin no.4 MCLR Reset input and Vpp programming voltage of a microcontroller Pin no.5 Vss Ground of power supply. Pin no.6 RB0 Zero pin on port B. Interrupt input is an additional function. ٦ Clock generator oscillator Oscillator circuit is used for providing a microcontroller with a clock. Clock is needed so that microcontroller could execute a program or program instructions PIC16F84 can work with four different configurations of an oscillator, two of them are crystal oscillator resistor-capacitor (RC) ٨

3 XT Oscillator Crystal oscillator is kept in metal housing with two pins, the operating frequency is written on housing. A 33pf ceramic capacitors are connected to gnd. Oscillator and capacitors can be packed in joint case with three pins, called ceramic resonator Oscillator clock divided by 4 can also be obtained on OSC2/CLKOUT pin, and can be used for testing or synchronizing other logical circuits Following a supply, oscillator starts oscillating. Oscillation at first has an unstable period and amplitude, but after some period of time it becomes stabilized ١١ RC Oscillator Resonant frequency of RC oscillator depends on supply voltage rate, resistance R, capacity C and working temperature. R value should be greater than 2.2K and less than 1M to avoid unstability Recommended R is between 3K and 100k capacitor should be above 20pF ١٠ To prevent such inaccurate clock from influencing microcontroller's performance, we need to keep the microcontroller in reset state during stabilization of oscillator's clock. ١٢ ٩

4 Reset Reset is used when microcontroller doesn't behave the way we want it to, interrupt in program execution, to get a microcontroller ready when loading a program. MCLR has to be connected via resistor to the positive supply pole, to prevent from bringing a logical zero to MCLR pin ١٣ Brown-out Reset Impulse for resetting is generated by microcontroller itself when supply doesn't drop to zero but falls below the limit that guarantees microcontroller's proper functioning (in a range from 1.2V to 1.8V) ١٥ sources of resets: Reset during power on, POR (Power-On Reset) Reset during regular work by bringing logical zero to MCLR microcontroller's pin. Reset during SLEEP regime Reset at watchdog timer (WDT) overflow Reset during at WDT overflow during SLEEP work regime. During a reset, RAM memory locations are not being reset. They are unknown during a power up and are not changed at any reset. SFR registers are reset to a starting position initial state. setting a program counter (PC) ١٤ to zero (0000h) That impulse lasts 72ms which is enough time for an oscillator to get stabilized. These 72ms are provided by an internal PWRT timer which has its own RC oscillator. ١٦

5 Central Processing Unit Central processing unit (CPU) is the brain of a microcontroller responsible for finding and fetching the right instruction which needs to be executed, decoding that instruction, finally its execution. Arithmetic logic unit is responsible for performing operations of adding, subtracting, moving, and logic operations, and shifting ١٧ Memory organization PIC16F84 has two separate memory blocks, one for data and the other for program Program memory 1024 locations with 14 bits width where locations zero and four are reserved for reset and interrupt vector. ١٩ In instructions with two operands, ordinarily one operand is in work register (W register), and the other is one of the registers (GPR, SFR ) or a constant. In instructions with one operand, is either W register or one of the registers. Execution of some instructions affects status bits, which depends on the result itself ALU can affect values of Carry (C), Digit Carry (DC), and Zero (Z) bits in STATUS register. ١٨ Data memory consists of EEPROM and RAM memories EEPROM memory consists of 64 eight bit locations RAM memory for data occupies space on a memory map from location 0x0C to 0x4F which comes to 68 locations. Locations of RAM memory are also called GPR registers which is an abbreviation for General Purpose Registers. ٢٠

6 GPR registers can be accessed regardless of which bank is selected at the moment. SFR registers first 12 locations in banks 0 and 1 are registers of specialized function assigned with certain blocks of the microcontroller. ٢١ Let's assume that we have selected bank 0 at the beginning of the program, and that we now want to write to certain register located in bank 1, say TRISB. Although we specified the name of the register TRISB, data will be actually stored to a bank 0 register at the appropriate address, which is PORTB in our example. Bcf STATUS, RP0 ;Select memory bank 0 Bsf STATUS, RP0 ;Select memory bank 1 ٢٣ Working with Memory Banks Memory Banks Selecting one of the banks is done via RP0 bit in STATUS register. Example: bcf STATUS, RP0 Instruction BCF clears bit RP0 (RP0=0) in STATUS register and thus sets up bank 0. bsf STATUS, RP0 Instruction BSF sets the bit RP0 (RP0=1) in STATUS register ٢٢ and thus sets up bank1. Locations 0Ch - 4Fh are general purpose registers (GPR) which are used as RAM memory. When locations 8Ch - CFh in Bank 1 are accessed, we actually access the exact same locations in Bank 0. In other words, whenever you wish to access one of the GPR registers, there is no need to worry about which bank we are in! ٢٤

7 Program Counter Program counter (PC) is a 13-bit register that contains the address of the instruction being executed 5-bit register PCLATH for the five higher bits of the address, and the 8-bit register PCL for the lower 8 bits of the address. ٢٥ bit 3 PD (Power-down bit) 1 = after supply has been turned on 0 = executing SLEEP instruction bit 2 Z (Zero bit) Indication of a zero result This bit is set when the result of an executed arithmetic bit 1 DC (Digit Carry) DC Transfer Bit affected by operations of addition, subtraction. 1 = transfer occurred on the fourth bit according to the order of the result 0 = transfer did not occur ٢٧ STATUS Register bits 6:5 RP1:RP0 (Register Bank Select bits) 01 = first bank 00 = zero bank bit 4 TO Time-out ; Watchdog overflow. 1 = overflow did not occur 0 = overflow did occur ٢٦ bit 0 C (Carry) Transfer Bit that is affected by operations of addition, subtraction and shifting. 1 = transfer occurred from the highest resulting bit 0 = transfer did not occur ٢٨

8 TRISB, PORTB, TRISA, and PORTA To change function of port to the following directions O O I O O O I I You need to write the following literal to TRIS register =0x ٢٩ Compiler directives LIST P=16f84a include "p16f84a.inc" config _FOSC_XT & _PWRTE_ON & _WDT_OFF & _CP_OFF ٣١ Assembly programming Compiler directives (MPLAP.X) Variables Values assignment Arithmetic operations Logic operations Loops Conditioning Branches Other instructions ٣٠ Variables As mentioned before PIC16F84 has three types of registers (memory) 1. W working register 2. SFR: Bank 00: 00h 0bh Bank 01: 80h 8bh ٣٢

9 2.1 Programmer can access SFR directly using its address (after selecting targeted bank) 0x00, 0x01,.., 0x0b 0x80, 0x81,, 0x8b 2.2 Programmer can assign name for SFR address INDF equ 0x00 PCL equ 0x02 STATUS equ 0x03 FSR equ 0x04 PCLATH equ 0x0A ٣٣ W EQU H'0000' F EQU H'0001' ;-----Bank INDF EQU H'0000' TMR0 EQU H'0001' PCL EQU H'0002' STATUS EQU H'0003' FSR EQU H'0004' PORTA EQU H'0005' PORTB EQU H'0006' EEDATA EQU H'0008' EEADR EQU H'0009' PCLATH EQU H'000A' INTCON EQU H'000B ;-----Bank OPTION_REG EQU H'0081' TRISA EQU H'0085' TRISB EQU H'0086' EECON1 EQU H'0088' EECON2 EQU H'0089 ٣٥ ;----- STATUS Bits C EQU H'0000' DC EQU H'0001' Z EQU H'0002' NOT_PD EQU H'0003' NOT_TO EQU H'0004' IRP EQU H'0007' RP0 EQU H'0005' RP1 EQU H'0006' ;----- PORTA Bits RA0 EQU H'0000' RA1 EQU H'0001' RA2 EQU H'0002' RA3 EQU H'0003' RA4 EQU H'0004' ;----- PORTB Bits RB0 EQU H'0000' RB1 EQU H'0001' RB2 EQU H'0002' RB3 EQU H'0003' RB4 EQU H'0004' RB5 EQU H'0005' RB6 EQU H'0006' RB7 EQU H'0007' Programmer can refer to Bits within registers Z equ 0x02 C equ 0x00 IRP equ 0x Programmer include processor.inc file include "p16f84.inc File path C:\Program Files (x86)\microchip\mplabx\mpasmx ٣٤ ;----- OPTION_REG Bits PSA EQU H'0003' T0SE EQU H'0004' T0CS EQU H'0005' INTEDG EQU H'0006' NOT_RBPU EQU H'0007' PS0 EQU H'0000' PS1 EQU H'0001' PS2 EQU H'0002' ;----- TRISA Bits TRISA0 EQU H'0000' TRISA1 EQU H'0001' TRISA2 EQU H'0002' TRISA3 EQU H'0003' TRISA4 EQU H'0004' ;----- TRISB Bits TRISB0 EQU H'0000' TRISB1 EQU H'0001' TRISB2 EQU H'0002' TRISB3 EQU H'0003' TRISB4 EQU H'0004' TRISB5 EQU H'0005' TRISB6 EQU H'0006' TRISB7 EQU H'0007' ٣٦

10 3. GPR Bank 00: 0ch 4fh Bank 01: 8ch cfh 3.1 Programmer can access GFR directly using its address (after selecting targeted bank) 3.2 Programmer can assign name for GPR address num1 equ 0x0c num2 equ 0x0d n equ 0x0e x equ 0x0f temperature equ 0x1A ٣٧ Arithmetic operations 8 ADDLW k Add W to a constant 9 SUBLW k Subtract W from a constant 10 ADDWF f,d Add W to f 11 SUBWF f,d Subtract W from f 12 INCF f,d Increment f 13 DECF f,d Decrement f ٣٩ Addlw H 12 Sublw D 12 Addwf b ,f addwf b ,1 Subwf b ,w subwf b ,0 Incf PORTB,f Decf PORTB,f Values assignment 1 MOVLW k Write constant in W register 2 MOVWF f Copy W to f 3 MOVF f,d Copy f to d 4 CLRW Write 0 in W 5 CLRF f Write 0 in f 6 BCF f,b Reset bit b in f 7 BSF f,b Set bit b in f MOVLW H'00' BSF STATUS,RP0 MOVWF TRISB BCF STATUS,RP0 ٣٨ Logic operations 14 ANDLW k Logic AND W with constant 15 IORLW k Logic OR W with constant 16 XORLW k Logic exclusive OR W with constant 17 ANDWF f,d Logic AND W with f 18 IORWF f,d Logic OR W with f 19 XORWF f,d Logic exclusive OR W with f 20 RLF f,d Rotate f to the left through CARRY 21 RRF f,d Rotate f to the right through CARRY 22COMF f,d Complement f 23SWAPF f,d Copy the nibbles from f to d crosswise ٤٠

11 Loops 24 INCFSZ f Increment f, skip if f =0 25 DECFSZ f Decrement f, skip if f = 0 MOVLW D'04' MOVWF 0x0c loop decfsz 0x0c goto loop ٤١ Branching 28 GOTO address Jump to address 29 CALL address Call a program 30 RETURN Return from a subprogram 31 RETLW Return from a subprogram with constant in W MOVLW D'04' MOVWF 0x0c loop call delay decfsz 0x0c goto loop ٤٣ delay nop nop nop return Conditioning 26 BTFSC f,b Test bit b in f, skip next instruction if b = 0 27 BTFSS f,b Test bit b in f, skip next instruction b =1 check btfsc PORTA,RA0 goto press_active_low goto check press_active_low ٤٢ Other instructions 32 NOP No operation 33 RETFIE Return from interrupt routine 34 CLRWDT Initialize watchdog timer 35 SLEEP Stand by mode ٤٤

12 Creating project ٤٥ ٤٦ ٤٧ ٤٨

13 ٤٩ ٥٠ ٥١ ٥٢

14 ٥٣ ٥٤ Working with simulator ٥٥ ٥٦

15 ٥٧ ٥٨ ٥٩ ٦٠

16 ٦١ ٦٢ ٦٣ ٦٤

17 Build delays DELAY MOVLW D'10' MOVWF 0x4f DELAY_loop DECFSZ 0x4f goto DELAY_loop RETURN ٦٥ PressControlledLedFlasher.asm LIST P=16f84 include "p16f84.inc" config _FOSC_XT & _PWRTE_ON & _WDT_OFF & _CP_OFF ORG 0 GOTO start ORG 4 GOTO start start BSF STATUS,RP0 MOVLW H'00' MOVWF TRISB MOVLW H'01' MOVWF TRISA BCF STATUS,RP0 LOOP MOVLW B' ' CALL DELAY BTFSs PORTA,RA0 GOTO LOOP MOVLW B' ' CALL DELAY GOTO LOOP ٦٧ LedFlasher.asm LIST P=16f84 include "p16f84.inc" config _FOSC_XT & _PWRTE_ON & _WDT_OFF & _CP_OFF ORG 0 GOTO start ORG 4 GOTO start start MOVLW H'00' BSF STATUS,RP0 MOVWF TRISB BCF STATUS,RP0 LOOP MOVLW B' ' CALL DELAY MOVLW B' ' CALL DELAY GOTO LOOP ٦٦ Fara7BentEl3omdah.asm LIST P=16f84 include "p16f84.inc" config _FOSC_XT & _PWRTE_ON & _WDT_OFF & _CP_OFF ORG 0 GOTO start ORG 4 GOTO start start MOVLW H'00' BSF STATUS,RP0 MOVWF TRISB BCF STATUS,RP0 CALL DELAY MOVLW B' ' CALL DELAY MOVLW B' ' CALL DELAY MOVLW B' ' GOTO LOOP ٦٨ LOOP CALL DELAY MOVLW B' '

18 PressControlledLedStatusToogle.as m LIST P=16f84 include "p16f84.inc" config _FOSC_XT & _PWRTE_ON & _WDT_OFF & _CP_OFF ORG 0 GOTO start ORG 4 GOTO start start BSF STATUS,RP0 MOVLW H'00' MOVWF TRISB MOVLW H'01' MOVWF TRISA BCF STATUS,RP0 MOVLW h'00' MOVWF 0X0C MOVLW B' ' ٦٩ LOOP CALL DELAY BTFSS PORTA,RA0 GOTO LOOP COMF 0X0C,F MOVF 0X0C,W GOTO LOOP ٧٠ Thanks,.. See you next week (ISA),