=========================================================== TALKING ELECTRONICS Interactive website http://www.talkingelectronics.com/ =========================================================== =========================================================== ROUTINES for "Copy and Pasting" by Colin Mitchell talking@tpg.com.au =========================================================== The following are the ROUTINES for "Copy and Pasting" into your program - commonly called your ".asm file." They are in alphabetical order, so everything is easy to find - and easy to use. Simply copy and paste them into your program: Hold the left mouse button down as you pass the mouse over the instructions. Then click the right mouse button and a box will appear. Select "Copy." Go to your program - in an another NotePad or WordPad - and "Paste" the instructions. All the instructions should "line-up" into three columns. If you use a set of instructions as a complete routine, it is called a sub-routine. Alternatively they can be added to another routine, such as "Main." Make sure you understand what to do before using this library. All these instructions are fully explained in "Library of Routines." The instructions for your program are arranged in three columns. The first column contains the "labels." They identify the first instruction for a sub-routine. The second column contains the "instruction" - called the mnemonic. The "half-computer" "half-English" instruction that both computer and micro understands. The third column contains the "comments." It must have a ";" before each line so that they are not assembled - so they don't appear in the final .hex file! Note: All the instructions in this library will "run" when placed in a program. But sometimes, something goes wrong. If an instruction has hidden "formatting," the assembler may create the wrong code. To see if an instruction has hidden formatting, simply hold down the left button on the mouse and drag across the instruction. The background will go black and will not extend past the actual word. Try the following: DECFSZ 1A,1 This instruction has hidden formatting: DECFSZ 1A,1 Simply remove any hidden formatting by holding the mouse on the unwanted spaces and use the back-space arrow to remove the spaces (or re-type the complete instruction) and the problem will be fixed. (It does not matter if "comments" have extra spaces. "Comments" are not assembled.) Start by copying TEMPLATE. Delete the unwanted instructions and add the instructions you want. Make sure the label is correct. ----------------------------------------------------- ADD A VALUE TO A FILE ----------------------------------------------------- A file contains a known value. To add a value to the file use: Add MOVLW 0CCh ;Put CCh into W ADDWF 0Eh ;CC will be added to the contents of file "E." If the file overflows, the Carry/Borrow bit in the Status file (file 03,0) will be SET. Add MOVLW 0CCh ;Put CCh into W ADDWF 0Eh ;CC will be added to the contents of file "E." BTFSS 03,0 ;Test the carry bit in the Status file GOTO AAA ;Micro will go to AAA if no overflow GOTO BBB ;Micro will go to BBB if overflow occurs ----------------------------------------------------- BEEP - TONE - this is a constant tone ----------------------------------------------------- To use RB0 as the output: MOVLW 01h (see line 8 in subroutine below) To use RB1 as the output: MOVLW 02h To use RB2 as the output: MOVLW 04h To use RB3 as the output: MOVLW 08h To use RB4 as the output: MOVLW 10h To use RB5 as the output: MOVLW 20h To use RB6 as the output: MOVLW 40h Tone MOVLW 40h ;The duration of the tone or "beep" MOVWF 1B Tone1 MOVLW A0h ;The length of HIGH and LOW - frequency of tone MOVLW 1A Tone2 NOP DECFSZ 1A,1 GOTO Tone2 MOVLW 80h ;Put 80 into W XORWF 06,1 ;XOR 80 with Port B. Toggle RB7 DECFSZ 1B,1 GOTO Tone1 RETURN ----------------------------------------------------- BEEP - BEEP - BEEP - repeat ----------------------------------------------------- This beep routine is suitable for debugging a program. The instruction GOTO Beep1 is inserted in a program to see how far the micro has advanced through the instructions. Beep1 produces an endless beep . . . beep . . . beep . . . In the sub-routine you are trying to debug, put the instruction: GOTO Beep1 At the beginning of memory, after Tables, put the following: Beep1 CALL Beep CALL BeepDel GOTO Beep1 Beep MOVLW 40h ;The duration of the beep MOVWF 1B Beep1 MOVLW A0h ;The length of HIGH and LOW - frequency of beep MOVLW 1A Beep2 NOP DECFSZ 1A,1 GOTO Beep2 MOVLW 80h ;Put 80 into W XORWF 06,1 ;XOR 80 with Port B. Toggle RB7 DECFSZ 1B,1 GOTO Beep1 RETURN BeepDel DECFSZ 1A,1 GOTO BeepDel DECFSZ 1B,1 GOTO BeepDel RETURN ----------------------------------------------------- BUTTON - SWITCH - PUSH BUTTON ----------------------------------------------------- In this routine a push button is connected to RA0. When it is pushed, a HIGH is delivered to RA0. To make RA1 a button-line, the second instruction in SetUp is: MOVLW 02. To make RA2 an input: MOVLW 04 The button-file must be cleared in SetUp. There are two flags. Bit0 in file 1F is the Debounce Flag and Bit1 in file 1F is the Button Pressed flag.  The microprocessor executes Main and CALLs Sw. If Sw detects a key-press, two flags are SET. The first is the Button Pressed flag and the second is the Debounce flag. The micro returns to Main and tests the Button Pressed flag to see if it is SET. If is is SET, the micro goes to a sub-routine such as CALL Increment, where a value can be incremented. The Button Pressed flag is then cleared and the micro CALLs Sw. If the switch is still pressed, the micro will return. The program is looking for the button to be released. When the button is released, the Sw sub-routine is ready to detect another button-push. SetUp BSF 03,5 ;Go to Bank 1 MOVLW 01 ;Put 01 into W to MOVWF 05 ; make RA0 input BCF 03,5 ;Go to Bank 0 CLRF 1F ;Clear the button-press file GOTO Main Sw1 BTFSS 05,0 ;Test the button. Button is "Active HIGH" GOTO Sw2 ;Button not pressed BTFSC 1F,0 ;Button pressed first time? Test debounce flag RETURN ;Button already pressed. Return to Main Sw1A DECFSZ 1A,1 ;Create short delay GOTO Sw1A ;Look again BTFSS 05,0 ;Is switch still pressed? GOTO Sw1B ;It was only noise BSF 1F,1 ;Button Pressed. Set button-pressed flag BSF 1F,0 ;Set debounce flag RETURN ;Return to Main Sw1B BCF 1F,0 ;Clear debounce flag RETURN ;Return to Main Main CALL Sw BTFSC 1F,1 ;Test button-press flag to see if button was pressed GOTO Main1 ;Button pressed Display the ;Button not pressed - carry out a sub-routine to values on a ; display values on a display etc. display etc. GOTO Main Main1 CALL Increment ;Increment the display. (you provide the routine) BCF 1F,1 ;Clear the button-press flag GOTO Main To connect two buttons to a micro. The second instruction in SetUp must be the addition of the hex values of the input lines E.g: RA1 and RA2 = 0000 0010 + 0000 0100 = 0000 0110 = 06h RA3 and RA5 = 0000 1000 + 0010 0000 = 0010 1000 = 28h SetUp BSF 03,5 ;Go to Bank 1 MOVLW 03 ;Put 03 into W to MOVWF 05 ; make RA0 and RA1 input BCF 03,5 ;Go to Bank 0 CLRF 1F ;Clear the button-press file GOTO Main Sw1 BTFSS 05,0 ;Test the first button. Button1 is "Active HIGH" GOTO Sw2 ;Button not pressed BTFSC 1F,0 ;Button pressed first time? Test debounce flag RETURN ;Button already pressed. Return to Main Sw1A DECFSZ 1A,1 ;Create short delay GOTO Sw1A ;Look again BTFSS 05,0 ;Is switch still pressed? GOTO Sw1B ;It was only noise BSF 1F,1 ;Button Pressed. Set button-pressed flag BSF 1F,0 ;Set debounce flag RETURN ;Return to Main Sw1B BCF 1F,0 ;Clear debounce flag RETURN ;Return to Main Sw2 BTFSS 05,0 ;Test the second button. Button2 is "Active HIGH" GOTO Sw2 ;Button not pressed BTFSC 1F,2 ;Button pressed first time? Test debounce flag RETURN ;Button already pressed. Return to Main Sw2A DECFSZ 1A,1 ;Create short delay GOTO Sw2A ;Look again BTFSS 05,0 ;Is switch still pressed? GOTO Sw2B ;It was only noise BSF 1F,3 ;Button Pressed. Set button-pressed flag BSF 1F,2 ;Set debounce flag RETURN ;Return to Main Sw2B BCF 1F,2 ;Clear debounce flag RETURN ;Return to Main Main CALL Sw1 BTFSC 1F,1 ;Test button-press flag to see if button was pressed GOTO Main1 ;Button pressed Display the ;Button not pressed - carry out a sub-routine to values on a ; display values on a display etc. display etc. CALL Sw2 BTFSC 1F,3 ;Test button-press flag to see if button was pressed GOTO Main2 ;Button pressed GOTO Main Main1 CALL Increment ;Increment the display. (you provide the routine) BCF 1F,1 ;Clear the button-press flag GOTO Main Main2 CALL Decrement ;Decrement the display. (you provide the routine) BCF 1F,3 ;Clear the button-press flag GOTO Main ----------------------------------------------------- CALLS - a list of suitable Calls: ----------------------------------------------------- Any names can be used. Keep the length to less than 8 letters. CALL Alarm CALL Beep CALL Button CALL Count CALL Dec CALL Delay CALL Display CALL Find CALL HeeHaw CALL Inc CALL Look CALL Loop CALL Main CALL Send CALL Show CALL Siren CALL Sound CALL Sw CALL Switch CALL Table CALL Test CALL Toggle CALL Tone ----------------------------------------------------- CALL A TABLE ----------------------------------------------------- Load a value into W and CALL Table1. The micro will look down the table. If the value you have loaded into W is 00, the first value in the table will be fetched. If the value is 01, the second value will be fetched. The micro adds the value in W to the Program Counter and this causes the micro to jump down the table. The PC naturally increments to the next instruction and that's why 3Fh is selected if the loaded value is 00. Table1 ADDWF 02h,1 ;Add W to the Program Counter to create a jump. RETLW 3Fh ;0    format= gfedcba RETLW 06h ;1 RETLW 5Bh ;2 RETLW 4Fh ;3 RETLW 66h ;4 RETLW 6Dh ;5 RETLW 7Dh ;6 RETLW 07h ;7 RETLW 7Fh ;8 RETLW 6Fh ;9 Main - - - - - MOVLW 00h ;load a value into W. 00h will pick up 3Fh from table CALL Table1 ;The micro will return with 3Fh in W MOVWF 06 ;Move 3Fh to output Port B (file 06) - - - - - - - - - - ----------------------------------------------------- DECREMENT A FILE ----------------------------------------------------- DECF 1A,1 ;Puts the new value into the file ----------------------------------------------------- DECREMENT A FILE and SKIP WHEN IT IS ZERO ----------------------------------------------------- DECFSZ 1A,1 ;Puts the new value into the file Not zero ;Goes here if file is not zero zero! ;Goes here if file is zero! ----------------------------------------------------- DELAYS ----------------------------------------------------- This delay creates FFh loops. Each loop takes 4uS Total time: 256 x 4 = 1024uS = say 1mS Del NOP DECFSZ 1A,1 ;Decrement file 1A GOTO Del ;Loop until file 1A is zero RETURN This delay creates 80h loops. Each loop takes 4uS Total time: 128 x 4 = 512uS Del MOVLW 80h ;Put 80h into W MOVWF 1A ;Copy 80h into file 1A DelA NOP DECFSZ 1A,1 ;Decrement file 1A GOTO DelA ;Loop until file 1A is zero RETURN NESTED DELAY This delay creates FFh loops (determined by file 1B). Each loop takes 4uS and there are 256 inner loops = 1024uS = 1mS This inner loop is executed 256 times via file 1B. Total time = 260mS Del NOP DECFSZ 1A,1 ;Decrement file 1A GOTO Del ;Loop until file 1A is zero DECFSZ 1B,1 ;Decrement file 1B GOTO Del ;Loop until file 1B is zero RETURN For a delay between 1mS and 260mS, you will need to pre-load file 1B: Del MOVLW 7Dh MOVLW 1B Del1 NOP DECFSZ 1A,1 ;Decrement file 1A GOTO Del1 ;Loop until file 1A is zero DECFSZ 1B,1 ;Decrement file 1B GOTO Del1 ;Loop until file 1B is zero RETURN ----------------------------------------------------- EEPROM ROUTINES ----------------------------------------------------- To load EEPROM: ORG 2100h   DE 84h, 16h, 23h, 80h, 0CAh, 32h, 7Bh, 0A2h  DE 34h, 53h, 25h, 02h, 0FFh, 20h, 03h, 04h  The sub-routine to read a value in the EEPROM is shown below. It reads EEPROM data at location specified in EEADR and returns the value in W EERead BSF Status, RP0 ;Go to Bank 1 BSF EECON1, RD ;Set the RD bit   BCF Status, RP0 ;Back to bank 0 MOVF 08, W ;EE Data is file 08.  Put into W RETURN The sub-routine to write to EEPROM is shown below.      Delay1 MOVLW 13h ;Create a 20mS delay MOVWF 1B ;20 loops Delay1a NOP DECFSZ 1A,1 ;4uS x 256 loops=approx 1mS GOTO Delay1a DECFSZ 1B GOTO Delay1a RETLW 00 EEWrite MOVWF 08 ;W to EEData BSF 03,5 ;Switch to bank 1 BCF 0B,7 ;Disable interrupts BSF 08,2 ;Write Enable bit set MOVLW 55h ;Toggle EEPROM Control  MOVWF 09 ;    Register bits MOVLW 0AAh ;Toggle EEPROM Control MOVWF 09 ;    Register bits BSF 08,1 ;Begin write sequence CALL Delay1 ;Call Delay1 BCF 08,2 ;Disable any further writes BSF 0B,7 ;Enable Interrupts BCF 03,5 ;Back to data bank 0 RETURN ----------------------------------------------------- GOTO ----------------------------------------------------- To make the micro go to another part of your program, use the GOTO instruction. Simply write the word "GOTO." Following GOTO, we place a "label" The label may be "Sw1" or "Count" or "Test." "Sw1" or "Count" or "Test." will appear in the first column of your program. The instruction "GOTO Test" will take the micro to the line containing the label: Test. The micro will not return to the instruction following GOTO Test, unless you have a label at the line such as "Togu1" and include an instruction GOTO Togu1 in your program. If you GOTO a sub-routine, the last instruction in the sub-routine cannot be RETURN as the micro does not have a return address in its memory - on the STACK. The only time a return address is placed on the stack is when a CALL is executed. GOTO Alarm GOTO Beep GOTO Button GOTO Count GOTO Dec GOTO Delay GOTO Display GOTO Find GOTO HeeHaw At the end of the sub-routine will be a GOTO Main or GOTO another sub-routine. It does not have to be the last instruction in a sub-routine but it is the only exit instruction you can use. You cannot use "RETURN." ----------------------------------------------------- HEX VALUES ----------------------------------------------------- All the files in a micro have 8 bits. All the input/output ports have 8 lines. The lowest bit or line is shown as a "1" in the folling value: 0000 0001 The lowest bit is called Bit0 The lowest line is called RA0 or RB0 or GP0 The next line (in/out line) or "bit" is called RA1, RB1 or GP1: 0000 0010 The lowest line has a value of zero when not active and ONE when active. The next has a vaue of TWO when active. The next has a value of FOUR when active. The next has a value of EIGHT when active. The 4 in/out lines have the following 16 possibilities: 0000 0001 0010 0011 0100 0101 0110 0111 1000 1001 1010 1011 1100 1101 1110 1111 They are given the following values: 0000 = 0 0001 = 1 0010 = 2 0011 = 3 0100 = 4 0101 = 5 0110 = 6 0111 = 7 1000 = 8 1001 = 9 1010 = A 1011 = B 1100 = C 1101 = D 1110 = E 1111 = F The four HIGH lines have the same format: 0000 0000 = 00 0001 0000 = 10 0010 0000 = 20 0011 0000 = 30 0100 0000 = 40 0101 0000 = 50 0110 0000 = 60 0111 0000 = 70 1000 0000 = 80 1001 0000 = 90 1010 0000 = A0 1011 0000 = B0 1100 0000 = C0 1101 0000 = D0 1110 0000 = E0 1111 0000 = F0 The four HIGH and LOW lines produce 256 combinations. Here are some: 0011 0101 = 35 1011 0000 = B0 1110 1001 = E9 1011 0000 = B0 0110 1110 = 6E 0101 0000 = 50 1001 1011 = 9B 0110 1011 = 6B The value to make RA2 and RA5 input: 0010 0100 = 24 ----------------------------------------------------- INCREMENT A FILE ----------------------------------------------------- INCF 1A,1 ;Puts the new value into the file ----------------------------------------------------- INPUT ----------------------------------------------------- To make a line (or lines), an INPUT, it must be given the value "1." This can be done anywhere in the program but it is best to put the instruction in SetUp. This makes it easy to locate when trouble-shooting. The instructions between BSF and BCF in the routine below are operating on a register in bank 1 and this is the in/out control register for PortA. It is NOT PortA. It is the register that determines the IN or OUT condition of each line in PortA and is called the TRIS register. SetUp BSF 03,5 ;Go to Bank 1 MOVLW 0F ;Put 0000 1111 into W to MOVWF 05 ; make RA0, RA1, RA2, and RA3 input BCF 03,5 ;Go to Bank 0 GOTO Main ----------------------------------------------------- INPUT A VALUE ----------------------------------------------------- The input lines for a 12C508A are: GP0, GP1, GP2, GP3, GP4 and GP5. GP3 is input-only and this line is usually the chosen input. The input lines for a PIC16F84A are: RA0,RA1,RA2,RA3,RA4,RA5,RA6,RA7. RB0,RB1,RB2,RB3,RB4,RB5,RB6,RB7. To input a value (A HIGH or LOW), make sure the line is an input. This is done in SetUp: SetUp BSF 03,5 ;Go to Bank 1 MOVLW 01 ;Put 0000 0001 into W to MOVWF 05 ; make RA0 input BCF 03,5 ;Go to Bank 0 GOTO Main In Main, test the input line: Main BTFSS 05,0 GOTO - - - - - - - - - - - - - ----------------------------------------------------- INVERT ----------------------------------------------------- An output line can be made an input (or vise versa) at any time during the running of a program. The following instructions work for both a PIC12C508A and a PIC16F84. The GPIO (General Purpose In/Out) lines on a PIC12C508A are GP0, GP1, GP2, GP3, GP4 and GP5, (GP3 as an input-only line). These lines correspond to RB0 to RB5 on a PIC16F84A. Suppose GP0 (RB0) is an output. To make GP0 (RB0) an input, use the following: Note: file 06 in bank1 is the TRIS file. It determines the input or output nature of each line in Port6. The lowest bit in the TRIS file is SET to make line RB0 an input. The line is then looked-at to see if it is HIGH and then the line is turned into an output. - - - - - - - - - - BSF 03,5 ;Go to Bank 1 BSF 06,0 ;Make the lowest bit in the TRIS file an input BCF 03,5 ;Go to Bank 0 BTFSC 06,0 ;Look at input line GP0 (RB0) GOTO xxxx ;GOTO xxxx if line RB0 is HIGH BSF 03,5 ;Go to Bank 1 BCF 06,0 ;Make the lowest bit in the TRIS file an output BCF 03,5 ;Go to Bank 0 - - - - - - - - - - ----------------------------------------------------- LAYOUT OF A PROGRAM ----------------------------------------------------- Use the following when layingout your program: SetUp Table1 Table2 LabelA - put all labels in alphabetical order so they can be found quickly. LabelB LabelC LabelD Main ----------------------------------------------------- LOOK for a Table-value ----------------------------------------------------- See Table-value ----------------------------------------------------- LOOP ----------------------------------------------------- When writing a program, you can use a loop to create a STOP function. Loop NOP GOTO Loop Inside the loop you can put a tone routine so you can see if the micro has reached the location. Loop MOVLW A0h ;The length of HIGH and LOW - frequency of tone MOVLW 1A Tone NOP DECFSZ 1A,1 GOTO Tone MOVLW 80h ;Put 80 into W XORWF 06,1 ;XOR 80 with Port B. Toggle RB7 GOTO Loop ----------------------------------------------------- MAIN ----------------------------------------------------- Main is the last routine in your program. It is a loop routine and has a number of CALL and/or GOTO instructions: (If you GOTO a sub-routine, the sub-routine must have a GOTO as the exit). Main - - - - - - - - - - - - - - - CALL Delay - - - - - - - - - - - - - - - GOTO Main ----------------------------------------------------- OUTPUT ----------------------------------------------------- To make a line (or lines), an OUTPUT, it must be given the value "0." This can be done anywhere in the program but it is best to put the instruction in SetUp. This makes it easy to locate when trouble-shooting. The instructions between BSF and BCF in the routine below are operating on a register in bank 1 and this is the in/out control register for PortB. It is NOT PortB. It is the register that determines the IN or OUT condition of each line in PortB and is called the TRIS register. SetUp BSF 03,5 ;Go to Bank 1 MOVLW 00 ;Put 0000 0000 into W to MOVWF 06 ; make all PortB lines output BCF 03,5 ;Go to Bank 0 GOTO Main In Main, output a HIGH on PortB (file 06): Main - - - - - MOVLW 0FFh ; MOVWF 06 ;Output a HIGH to the 8 lines of PortB - - - - - - - - - - ----------------------------------------------------- OVERFLOW ----------------------------------------------------- If a value is added to a file, overflow may occur. To see if overflow occurs, test the Carry/Borrow bit in the Status file (file 03,0). It will be SET if overflow occurs. Add MOVLW 0CCh ;Put CCh into W ADDWF 0Eh ;CC will be added to the contents of file "E." BTFSS 03,0 ;Test the carry bit in the Status file GOTO AAA ;Micro will go to AAA if no overflow GOTO BBB ;Micro will go to BBB if overflow occurs ----------------------------------------------------- RETURN ----------------------------------------------------- The PIC12C508A does not have a RETURN instruction. If you use RETURN in your program, the assembler will replace it with RETLW 00 when creating a .hex file for a PIC12C508A. ----------------------------------------------------- REVERSE ----------------------------------------------------- An output line can be made an input (or vise versa) at any time during the running of a program. The following instructions work for both a PIC12C508A and a PIC16F84. The GPIO (General Purpose In/Out) lines on a PIC12C508A are GP0, GP1, GP2, GP3, GP4 and GP5, (GP3 as an input-only line). These lines correspond to RB0 to RB5 on a PIC16F84A. Suppose GP0 (RB0) is an output. To make GP0 (RB0) an input, use the following: Note: file 06 in bank1 is the TRIS file. It determines the input or output nature of each line in Port6. The lowest bit in the TRIS file is SET to make line RB0 an input. The line is then looked-at to see if it is HIGH and then the line is turned into an output. - - - - - - - - - - BSF 03,5 ;Go to Bank 1 BSF 06,0 ;Make the lowest bit in the TRIS file an input BCF 03,5 ;Go to Bank 0 BTFSC 06,0 ;Look at input line GP0 (RB0) GOTO xxxx ;GOTO xxxx if line RB0 is HIGH BSF 03,5 ;Go to Bank 1 BCF 06,0 ;Make the lowest bit in the TRIS file an output BCF 03,5 ;Go to Bank 0 - - - - - - - - - - ----------------------------------------------------- SetUp ----------------------------------------------------- This is the first sub-routine in your program. It sets up the port (or ports) in the microcontroller. A port has up to 8 lines and these can be inputs or outputs. (GP3 for a PIC12C508A can be input-only). The input lines for a 12C508A are: GP0, GP1, GP2, GP3, GP4 and GP5. GP3 is input-only and this line is usually the chosen input. The output lines for a 12C508A are: GP0, GP1, GP2, GP4 and GP5. An input line can be changed to an output at any time during the running of a program. An output line can be changed to an input at any time during the running of a program. The input/output lines of a PIC12C508A are in file 06. To make GP0 an input, place the following instructions in SetUp: SetUp BSF 03,5 ;Go to Bank 1 MOVLW 01 ;Put 0000 0001 into W to MOVWF 06 ; make GP0 input BCF 03,5 ;Go to Bank 0 GOTO Main To make GP0 an output, place the following instructions in SetUp: SetUp BSF 03,5 ;Go to Bank 1 MOVLW 00 ;Put 0000 0000 into W to MOVWF 06 ; make GP0 input BCF 03,5 ;Go to Bank 0 GOTO Main To make any GP line an input, place "1" in the corresponding position for the value loaded into W: SetUp BSF 03,5 ;Go to Bank 1 MOVLW 08 ;Put 0000 1000 into W to MOVWF 06 ; make GP3 input BCF 03,5 ;Go to Bank 0 GOTO Main To create two input lines: SetUp BSF 03,5 ;Go to Bank 1 MOVLW 12 ;Put 0001 0010 into W to MOVWF 06 ; make GP1 and GP4 input BCF 03,5 ;Go to Bank 0 GOTO Main The input lines for a PIC16F84A are: RA0,RA1,RA2,RA3,RA4,RA5,RA6,RA7. RB0,RB1,RB2,RB3,RB4,RB5,RB6,RB7. SetUp BSF 03,5 ;Go to Bank 1 MOVLW 03 ;Put 03 into W to MOVWF 05 ; make RA0 and RA1 input BCF 03,5 ;Go to Bank 0 GOTO Main ----------------------------------------------------- STATUS FILE ----------------------------------------------------- The STATUS file is file 03. Bit0 is the Carry/Borrow Bit1 is the Digit Carry/Borrow Bit2 is the Zero bit Bit3 is the Power Down bit Bit4 is the Time-out bit When bit5 is SET Bank1 is selected When bit5 is CLEAR Bank0 is selected ----------------------------------------------------- STOP ----------------------------------------------------- The micro does not have a STOP or HALT instruction. When writing a program, you can use a loop to create a STOP function. Loop NOP GOTO Loop Inside the loop you can put a tone routine so you can see if the micro has reached the location. Loop MOVLW A0h ;The length of HIGH and LOW - frequency of tone MOVLW 1A Tone NOP DECFSZ 1A,1 GOTO Tone MOVLW 80h ;Put 80 into W XORWF 06,1 ;XOR 80 with Port B. Toggle RB7 GOTO Loop ----------------------------------------------------- TABLE - see also CALL A TABLE ----------------------------------------------------- Load a value into W and CALL Table1. The micro will look down the table. If the value is 00, the first value in the table will be fetched. If the value is 01, the second value will be fetched. The micro adds the loaded-value into the Program Counter and this causes the micro to jump down the table. The PC naturally increments and that's why 3Fh is selected if the loaded value is 00. Any values with a letter as the first part of the hex value must begin with a "0" E.g: FFh = 0FFh CDh = 0CDh The end of a table can be identified by using 0FFh (providing FFh is not a required table value). In Main, look for 0FFh as a table value. Table1 ADDWF 02h,1 ;Add W to the Program Counter to create a jump. RETLW 3Fh ;0    format= gfedcba RETLW 06h ;1 RETLW 5Bh ;2 RETLW 4Fh ;3 RETLW 66h ;4 RETLW 6Dh ;5 RETLW 7Dh ;6 RETLW 07h ;7 RETLW 7Fh ;8 RETLW 6Fh ;9 RETLW 0FFh Main - - - - - MOVLW 00h ;load a value into W. 00h will pick up 3Fh from table CALL Table1 ;The micro will return with 3Fh in W MOVWF 06 ;Move 3Fh to output Port B (file 06) - - - - - - - - - - ----------------------------------------------------- Table-value ----------------------------------------------------- To "Look for" or "fetch" a table value, you need 2 instructions. To fetch the first table value, load W with 00. To fetch the second table value, load W with 01 etc. The second instruction is CALL Table1 The micro will return with the table-value in W: Table1 ADDWF 02h,1 ;Add W to the Program Counter to create a jump. RETLW 3Fh ;0    format= gfedcba RETLW 06h ;1 RETLW 5Bh ;2 RETLW 4Fh ;3 RETLW 66h ;4 RETLW 6Dh ;5 RETLW 7Dh ;6 Main - - - - - - - - - - MOVLW 04 CALL Table1 - - - - - - - - - - The micro will return with 66h in W ----------------------------------------------------- TEMPLATE ----------------------------------------------------- Use this template as a start to writing your program. This is not a fully-functional program. It is a set of example-instructions. Delete the unwanted instructions. ;Expt1.asm ;Project: Turning on a ----- ;This program can be assembled for a PIC12C508A or PIC16F84 ORG 0 ;This is the start of memory for the program SetUp BSF 03,5 ;Go to Bank 1 MOVLW 01 ;Load W with 0000 0001 MOVWF 05 ;Make RA0 input MOVLW 01 ;Load W with 0000 0001 MOVWF 06 ;Make RB0 or GP0 input BCF 03,5 ;Go to Bank 0 - the program memory area GOTO Main Delay NOP ;Create approx 250mS delay DECFSZ 1A,1 GOTO Delay DECFSZ 1B,1 GOTO Delay RETURN Look CLRF 0C ;Count-down file - - - - - CALL Delay ;250mS delay BSF 03,5 ;Go to Bank 1 MOVLW 04 ;Load W with 0000 0100 MOVWF 05 ;Make RA2 input & RA3 output BCF 03,5 ;Go to Bank 0 - the program memory area. RETURN Main BTFSS 05,0 ;Test the input line on port A GOTO Main2 ;Button not pressed BSF 06,0 ;Button pressed. Turn on LED CALL Delay - - - - - CALL Look Main2 BCF 06,0 ;Button not pressed. Turn off LED GOTO Main ;Loop Main END ;Tells assembler end of program ----------------------------------------------------- TOGGLE ----------------------------------------------------- Toggle changes the state of an output. You do not have to know the state of the output before the operation. The output changes from HIGH to LOW or LOW to HIGH. You do not know the output after the operation. This operation is not suitable if you want to leave an output low when not in use so that the output current is low. To toggle RB0 use: MOVLW 01h (see line 8 in subroutine below) To toggle RB1 use: MOVLW 02h To toggle RB2 use: MOVLW 04h To toggle RB3 use: MOVLW 08h To toggle RB4 use: MOVLW 10h To toggle RB5 use: MOVLW 20h To toggle RB6 use: MOVLW 40h Toggle MOVLW 80h ;Put 80 into W XORWF 06,1 ;XOR 80 with Port B. Toggle RB7 ----------------------------------------------------- TRIS ----------------------------------------------------- "Tris" is the file (register) that determines if each bit in a Port is input or output. See Library of Routines for more details.