PIC Discussion By Eng. Tamar Jomaa

Transcription

1 PIC Discussion By Eng. Tamar Jomaa

2 Outlines 2.6 TMR0 2.7 EEPROM 2.8 Look up table 2.9 Macro

3 2.6 TMR0 Example#1 Write an assembly program to make a counter using TMR0, the count should increment it s value on every 2 push buttons on RA4.

4 Solution: Example#1 bit bit0 0 Bit7:portb pull-up are enabled. Bit6:interrupt in falling edge of RB0/INT Bit5:TMR0 clock source on RA4/TOCKI Bit4:TMR0 at the falling edge. Bit3:prescaler is assigned to WDT Bit[0,1,2]:prescaler is 1:2

5 2.6 TMR0 Example#2 Write an assembly program to make a counter. The counter increments it s value from 0-9 every 1 sec delay, using TMR0 delay technique.

6 Solution: Example# Bit7:portb pull-up are enabled. Bit6:interrupt in falling edge of RB0/INT Bit5:TMR0 clock source on internal clock Bit4:TMR0 at the rising edge. Bit3:prescaler is assigned to TMR0 Bit[0,1,2]:prescaler is 1:256

7 Solution: Example#2 Note: Delay rule: Num: according to prescaler assignment 256: because TMR0 counts from Num1: constant value The maximum delay is: It will happen when num=7 & num1=255. So the delay=265 x 256 x 255x[4/4M]=16.7sec. Example: we want to make delay 5sec, we should assume one and find the other If num=7 num1=76 For delay 1 sec: num=7 num1=15.

8 2.7 EEPROM The following registers relate to EEPROM operations: 1. EEDATA holds the data byte to be read or written. 2. EEADR contains the EEPROM address to be accessed by the read or write operation. 3. EECON1 contains the control bits for EEPROM operations. 4.EECON2 protects EEPROM memory from accidental access. This is not a physical register..

9 EECON1 (ADDRESS 88h) 2.7 EEPROM

10 2.7 EEPROM Writing to EEPROM memory 1. Put the address which you want to write in EEADR. 2. Put the data you want to write in EEDATA. 3. Disable all interrupts(gie=0) to avoid errors. 4. Set the bin WREN in EECON1. 5. Keys: Write 0X55 in EECON2. Write 0XAA in EECON2. 6. Set the bin WR in EECON1, after this step the data will transfer from EEDATA to the specified address in EEADR. 7. Wait until writing operation is finished. 8. Enable all interrupts(gie=1). Note: These steps will be the same in every writing process, the only things will change are the address which you want to write to it and the data you want write it.

11 2.7 EEPROM Writing to EEPROM memory Example of the part of a program which writes data 0xEE to first location in EEPROM memory could look something like the following: BSF STATUS, RP0 ; Bank 1 BCF INTCON, GIE ;Disable INTs. BSF EECON1, WREN ; Enable Write MOVLW 55h MOVWF EECON2 ; Write 55h MOVLW AAh MOVWF EECON2 ; Write AAh BSF EECON1,WR ; Set WR bit ; Begin write BSF INTCON, GIE ; Enable INTs

12 2.7 EEPROM Reading from EEPROM memory 1) Put the address which you want to read from EEADR. 2) Set the bin RD in EECON1. 3) Move the data which was read from EEDATA to work register.

13 2.7 EEPROM Reading from EEPROM memory Sample of the part of a program which reads data in EEPROM, could look something like the following: BCF STATUS,RP0 ; Bank 0 MOVLW CONFIG_ADDR MOVWF EEADR ; Address to read BSF STATUS,RP0 ; Bank 1 BSF EECON1, RD ; EE Read BCFSTATUS, RP0 ; Bank 0 MOVF EEDATA, W ; W = EEDATA

14 2.7 EEPROM Complete Example: The following example shows how to handle with the EEPROM data memory, it is consisting of four pin DIP switch to be used to enter the data to the EEPROM memory, then a single switch to read the written data to the output port(portb) which connects four LEDs to it.

15 Complete Example: 2.7 EEPROM

16 Complete Example: 2.7 EEPROM

17 Complete Example: 2.7 EEPROM

18 2.8 Look up table A look up table(lut) is used to change data from one form to another i.e pounds to kilograms, 8C to 8F, inches to centimeters etc. The explanation of it is used when being disable to find a special relation between the input and the output in any way. The idea of the LUT is to store the wanted data which will be the output in the FSR register in the same sequence as desired to appear. The statements:movlw 0Fh ANDWF PORTA,W are used to view the desired numbers only. This operation is called masking, It enables us to view the wanted numbers and hide or cover the unwanted digits. It is applied by ANDing the wanted with ones and the unwanted with zeros.

19 2.8 Look up table The following example show how to make a look up table, and displaying the results on a 7-segment.

20 2.8 Look up table

21 2.8 Look up table

22 2.8 Look up table

23 2.9 Macro Macros are user defined group of instructions which will enter assembler program where macro was called. It is possible to write a program even without using macros. But with their use written program is much more readable, especially if more programmers are working on the same program together. Macros have the same purpose as functions of higher program languages.

24 2.9 Macro How to write macros? <label>macro[<argument1>,<argument2>,...<argumentn>] Endm In order to use a macro in the program, it is necessary to include macro file in the main program with instruction include "macro_name.inc".

25 2.9 Macro What's the difference between macro and subroutine? 1)In execution stage, the subroutine puts the address of the called function in PC and hide the original value of PC (before calling) in the stack. 2) The macro in compilation process (not in execution), copies the macro in the place where it is called. It doesn't put address on stack. 3) The subroutine can be written or called in any place, but the macro must be declared before calling.

26 2.9 Macro What's the difference between macro and subroutine? 4) In subroutine, some statements may be passed on it more than once. In macro, passes on statements only one time. 5) The subroutine takes more time in execution, but the macro doesn't take time. This van be considered as an advantage to the macro. 6) The subroutine doesn't take size in the program, but the macro takes as it is copied in the program during calling. It is considered as disadvantage to the macro.

27 Using Macros internally

28 Using Macros internally

29 Using Macros internally

30 Using Macros externally:

31 Using Macros externally:

32 Using Macros externally:

33 Using Macros externally:

34 2.9 Macro: Notes: The first Macro is declared internally in the same file, but the second Macro is declared externally. In calling Macros, we didn't write the command call or other commands. We call it by writing its name directly. The program with internally or externally macro is the same size. Externally macros must be included in the same folder of the main program in which it is called, or writing its extension in the include statement.

35 Be free to ask me any question