THE PROGRAM
One of the first things to organise is the detection of the tactile switches.
These switches are detected by a circuit called a TIME DELAY, made up of a "resistor and capacitor" in series.
When a resistor and capacitor are connected in series, it takes a certain period of time to charge the capacitor (and also discharge it).
When the capacitor value is very small and the resistor is large, this time-interval will be very small, but when we are using a microcontroller to detect this interval of time, we can measure in microseconds.
You can see the capacitor is connected to a chain of resistors in the circuit above and one line (called a port-line) from the micro is connected to the capacitor.
The routine starts by the micro making the port-line an output and creating a HIGH on the line. This charges the capacitor and then the micro turns the line into an input and monitors it to see when the capacitor is discharged.
At the moment, the capacitor is connected to the full string of resistors that are not connected to 0v rail and the timing will be long (in the order of many microseconds). The program neglects this reading and classifies it as "no switch pressed."
But if a switch (also called a button) is pressed, the time will be reduced and this timing is detected by the sub-routine.


TESTING THE SWITCHES
The first program we produce to do this is called a TEST PROGRAM or TEST ROUTINE to find out the number of  microseconds for each switch. Each group of 6 microseconds will increment a register called "flashes" and this value is used in our program to detect the particular switch.
This test program is called Test-1.asm
Since the value of the capacitor may have very wide tolerance, our Test Program will generated a value for the capacitor you have used and you must make sure it corresponds with our value.
This is especially noticeable for switch 4 with 10 units of "timing."
To check the value for the switches, button 1 is pressed BEFORE the circuit is turned ON. The circuit is turned ON and the button is released after 1 second (it odes not matter if the switch is released or not). The LED will flash 10 times for button 1. Repeat this for buttons 2, 3, 4 and 5. The LED will flash 7, 5 and 3 times for the other switches. Make sure the LED flashes the same number of times for the capacitor you have used, so the switches will be detected correctly. If not, button 1 will be detected when button 2 is pressed or button 2 will be detected when button 1 is pressed.
The switches are now ready to be detected.


TESTING THE 8x8 MODULE
After building the 8x8 module (containing the 8x8 display and MAX 7219 chip), you will want to get something on the display.
The chip contains 8 registers. Each register holds 8 bits to show the 64 bits of information for the screen and 5 other registers to hold information to:
Decode mode - used for 7-segment displays - not used for 8x8 display    address 9h
Intensity - determines the brightness of the screen    address 0Ah
Scan Limit  - used for  3 x 7Sement displays   address 0Bh
Shutdown -  turn the display ON or turn it OFF   address 0Ch
Test Display  - turns on all LEDs   address 0Fh
To get something on the screen, you need to produce 3 sub-routines.
These are contained in Test-2.asm
The first sub-routine loads the address and data to create a column of illuminated LEDs.
The top LED has the value 01. The next LED: 02, 04 08 102040 and the bottom LED 80.
We have used the value 0AAh for column 7 and this means the 2nd 4th 6th and 8th LED will be illuminated.
Don't worry about the other columns. They will be showing JUNK from the other 7 registers as the chip does not clear the registers when it is turned ON.
The next sub-routine in Test-2.asm creates to non-shut-down mode. This make sure the display will illuminates the LEDs.
The next sub-routine tells the chip to scan all 8 columns.
We have added 100mS delays between each of the clock pulses so you can see the chip receiving the data and clock pulses.
Three LEDs are added to the PC board on lines Data, Chip Select and Clock to observe the signals entering the chip.
This is an important aid to getting the circuit to work correctly, if the display fails to illuminate. 
As soon as this information is passed to the chip and Chip Select is taken HIGH, the display will scan.

In Test-3.asm we remove the 100mS delays and see the display illuminate immediately.

Three things we learnt from the "delayed routine:"
1. The chip works at low clock-rate.
2. A small delay must be added between changing bits on the output port. This applies to changing a bit in any PIC register and then wanting to change another bit in the same register. The chip required 300uS between commands for this operation to be reliable (in our routine).
3. The MAX chip must be closed after each sub-routine and opened for the next sub-routine.   

We can now "drive the display" and the rest of the program can be created to show letters and numbers on the display as well as detect the buttons to Increment the Display (button 1), Decrement the Display (button 2), Store the values (button 3) and "RUN" the message across the display (button 4). 

CREATING A RUNNING MESSAGE
Each letter and number uses the 6 middle columns.
This means 6 bytes are required from a table.
The program puts the first byte of a letter into location 48h and a sub-routine shifts the data from location 48h to 47h.
When you push "Run" the display is blank but the shift sub-routine takes the data from 41h and places it is 40h. Then 42h to 41h etc to finally transferring 48h to 747h. This creates the shift on the screen. 
The program then sends the 8 bytes to the 8x8 Display and calls 200mS delay to show the screen.
The program then places the second byte into location 48h and shifts the data to the left.
The data is then sent to the display and shown on the screen for 200mS.
This continues for the 6 bytes of the letter and then the EEPROM is accessed for the address in table1 for the next letter.

The data is shifted LEFT

When all the letters in the message have been displayed, the program starts from the beginning of EEPROM memory and repeats the message.
The hex value for each pixel is shown in the diagram above. These values are needed when you want to create your own images on the display. The table above shows 256 images and the link provides the .hex values for each image.

ICSP FAILURE (In-Circuit Serial Programming Failure)
Sometimes a chip will fail to program on the 6th or 10th programming and it will not program on further attempts.
The reason is one of the cells inside the chip is preventing the signal being recognised by the programmer.
You need to remove the chip from the project so all voltage is removed from the chip to reset the cells, or you can swap the chip for another.
Another problem with ICSP is the fact that the chip starts to run the program in its memory as soon as the programmer is connected and if any of the outputs co-inside with the programming lines, you will get a clash that prevents the programmer recognising the chip.
 

THE SWITCHES  -  BUTTONS
The project has 4 tactile switches - UP  - DOWN - STORE - RUN
The first switch increments the alphabet and numbers.
The second switch decrements the letters and numbers.
The third switch allows you to store the letter showing on the screen.   
The fourth switch creates a RUNNING MESSAGE on the 8x8 DISPLAY.
To delete the message, press RUN before turning the project ON.
Turn the project OFF. The next time it is turned ON, the letter-counter has already been set to zero.
When writing a message, the last character must be a "space" to make the message easy to read.
When the project is turned off, and turned ON again, the message can be played on the display by pushing "Run."
You can add to the message by turning the project off then on again and adding letters.
Messages can be as long as 255 letters. The program does not detect when memory is full. You need to keep track.

PROGRAMMING THE CHIP
The chip comes pre-programmed when you buy the Running Display kit, however if you want to program your won chip or make modifications to the chip in the kit, you will need to add the In-Circuit Programming pins shown in the photo above.
The following circuit shows the connections of the 5 lines from the programming socket to the chip:

ADDING SUB-ROUTINES TO THE PROGRAM
The program is created by adding a few lines of code then testing the result.
It is saved with a new name so you can go back to previous developments, if something does not work.
Our system of "copy-and-paste" (from other programs and our Library of Subroutines) will help you develop each routine. The library will also answer many of your questions.
It consists of 3 pages:
A-E  E-P  P-Z
You will notice we added 3 LEDs to the lines on our development board to observe the clock, data and chip select lines.
By adding delays in the program you can see the number of clock pulses to confirm the information is being correctly transferred.
This was essential in getting the 8x8 Dot Matrix Module to display the characters as it requires a number of routines to set-up the MAX chip.
By using assembly-mode for creating a program, you can see exactly what happens at each stage of testing a new set of instructions and it eliminates a lot of frustration. You don't have to learn any high-level language and you are not left wondering how to write an instruction or what is actually happening. All the assembly instructions are provided in a list with their explanation.
See INSTRUCTION SET.
Our method is the simplest way to produce a program and is ideal for beginners. There are only about 35 instructions you need to remember to produce a program plus about 100 other instructions to "set-up" various conditions.
This is called "HAND CODING" and is suitable for a program up to about 1,000 instructions.
The 8x8 Module program is just over 350 instructions long, with a 250 byte table, so  you can see how much can be contained in this very small microcontroller.
A completely new set of characters can be shown on the display and this program can be access by pressing switch A before turning on the project. This will access the new program and you have just over 400 locations available for sub-routines and a table. 
You can add 6 more characters to the table to be within the 256 byte boundary or produce a completely new table.
Even though this will give you less than 150 bytes for programming, you can achieve a lot of effects because you will be able to CALL already-prepared sub-routines.
This project shows you how to connect a number of switches to a single port-line, how to drive a MAX chip, how to create running messages on the 8x8 dot matrix display and how to store data in the EEPROM.
All these are valuable "building-blocks" for the time when you want to design your own project.


THE FILES:
test-1.asm  .txt    .hex
test-2.asm  .txt    .hex
test-3.asm  .txt    .hex
8x8 Display.asm
8x8 Display.txt
8x8 Display.hex

Do not put the following program into Notebook 2. Use the .asm file above. The following program may have formatting problems and it may not compile properly. Compiling is done with MPASM to produce .hex file (as well as other helpful files).

;******************************* ;;8x8 Module.asm ; ; 23-6-2013 ;******************************* list p=12F629 radix dec include "p12f629.inc" errorlevel -302 ; Don't complain about ;BANK 1 Registers during assembly __CONFIG _MCLRE_OFF & _CP_OFF & _WDT_OFF & _INTRC_OSC_NOCLKOUT ;_MCLRE_OFF - master clear must be off for gp3 to work as input pin ;**************************************************************** ; variables - names and files ;**************************************************************** Cblock 20h temp1 ;used in delays temp2 ;used in delays temp3 ;used in EEPROM data fetching temp4 ;used in EEPROM data fetching temp5 ;used in EEPROM data fetching temp6 ;used in EEPROM data fetching current ;holds current EEPROM location letters ;letters holds the number of letters in EEPROM serial address _data jump ;table1 jump value columns ;for 6 columns Sw_Flag ;detecting sw-press eefile ;total number of characters in EEPROM endc ;**************************************************************** ;Equates ;**************************************************************** status equ 0x03 rp1 equ 0x06 rp0 equ 0x05 GPIO equ 0x05 status equ 03h option_reg equ 81h ; bits on GPIO pin7 equ 0 ;GP0 LED - flashes to indicate key number pin6 equ 1 ;GP1 Data to 8x8 Module pin5 equ 2 ;GP2 Chip Select pin4 equ 3 ;GP3 pin3 equ 4 ;GP4 Clock pin2 equ 5 ;GP5 4 switches ;bits rp0 equ 5 ;bit 5 of the status register ;**************************************************************** ;Beginning of program ;**************************************************************** org 0x00 goto SetUp ;**************************************************************** ;Table ;**************************************************************** table1 addwf 02h,1 ;add W to program counter dt 7Eh,09h,09h,09h,7Eh,00h ;A dt 7Fh,49h,49h,49h,36h,00h ;B dt 3Eh,41h,41h,41h,22h,00h ;C dt 7Fh,41h,41h,22h,1Ch,00h ;D dt 7Fh,49h,49h,41h,00h,00h ;E dt 7Fh,09h,09h,01h,00h,00h ;F dt 3Eh,41h,49h,49h,3Ah,00h ;G dt 7Fh,08h,08h,08h,7Fh,00h ;H dt 7Fh,00h,00h,00h,00h,00h ;I dt 20h,40h,40h,3Fh,00h,00h ;J dt 7Fh,08h,14h,22h,41h,00h ;K dt 7Fh,40h,40h,40h,00h,00h ;L dt 7Fh,06h,18h,18h,06h,7Fh ;M dt 7Fh,02h,0Ch,18h,20h,7Fh ;N dt 3Eh,41h,41h,41h,3Eh,00h ;O dt 7Fh,09h,09h,09h,06h,00h ;P dt 1Eh,21h,31h,21h,5Eh,00h ;Q dt 7Fh,09h,19h,29h,46h,00h ;R dt 26h,49h,49h,49h,32h,00h ;S dt 01h,01h,7Fh,01h,01h,00h ;T dt 3Fh,40h,40h,40h,3Fh,00h ;U dt 0Fh,30h,40h,30h,0Fh,00h ;V dt 3Fh,40h,38h,40h,3Fh,00h ;W dt 63h,14h,08h,14h,63h,00h ;X dt 03h,0Ch,70h,0Ch,03h,00h ;Y dt 61h,51h,49h,45h,43h,00h ;Z dt 42h,7Fh,40h,00h,00h,00h ;1 dt 72h,49h,49h,49h,46h,00h ;2 dt 22h,41h,49h,49h,36h,00h ;3 dt 18h,14h,12h,7Fh,10h,00h ;4 dt 2Fh,49h,49h,49h,31h,00h ;5 dt 3Eh,49h,49h,49h,32h,00h ;6 dt 01h,71h,09h,05h,03h,00h ;7 dt 36h,49h,49h,49h,36h,00h ;8 dt 26h,49h,49h,49h,3Eh,00h ;9 dt 00h,00h,00h,00h,00h,00h ;space (0D8h) ;**************************************************************** ;Set Up ;**************************************************************** SetUp bsf status, rp0 ;Bank 1 movlw b'11001000' ;Set TRIS GP0,1,2,4,5 out GP3 not used movwf TRISIO bcf status, rp0 ;bank 0 movlw 07h ;turn off Comparator ports movwf CMCON ;must be placed in bank 0 clrf GPIO ;Clear GPIO of junk clrf jump clrf 40h ;clear files for RUN clrf 41h clrf 42h clrf 43h clrf 44h clrf 45h clrf 46h clrf 47h ;Delete EEPROM Data - pressing "RUN" before switch-ON ;deletes DATA by zeroing the number of letters in address 07h call SwPressed btfss Sw_Flag,4 ;see if "Run" switch pressed goto Main ;not pressed movlw 7Fh bsf status,rp0 ;select bank1 movwf eeadr bcf status,rp0 ;select bank0 clrw bsf status,rp0 ;select bank1 movwf eedata bcf status,rp0 ;select bank0 call write call SwPressed btfsc Sw_Flag,4 ;see if "Run" switch not pressed goto $-2 goto Main ;**************************************************************** ;* Delays * ;**************************************************************** _6uS goto $+1 retlw 00 _12uS goto $+1 goto $+1 goto $+1 goto $+1 retlw 00 _1mS nop decfsz temp1,f goto $-2 retlw 00 _10mS movlw .10 movwf temp2 call _1mS decfsz temp2,f goto $-2 retlw 00 _50mS movlw .50 movwf temp2 _50 nop decfsz temp1,f goto _50 decfsz temp2,f goto _50 retlw 00 _100mS movlw .100 movwf temp2 _100 nop decfsz temp1,f goto _100 decfsz temp2,f goto _100 retlw 00 ;**************************************************************** ;* Sub Routines * ;**************************************************************** Dec_Jump decf jump,f decf jump,f decf jump,f decf jump,f decf jump,f decf jump,f retlw 00 ;creates blank column 1,data for cols:234567 and blank col8 Display movlw 0D8h ;Look for end of table xorwf Jump,w btfss status,z ;zero bit will be set if the same goto $+2 clrf jump ;start at top of table clrf address incf address,1 ;col1 = address 1 clrf _data call Load movlw 6 movwf columns ;load counter for 6 columns incf address,1 movf Jump,w ;move jump value into w call table1 ;get jump value for table1 movwf _data ;load data from table1 into _data call Load incf jump,1 ;increment jump value for table1 decfsz columns,f goto $-7 incf address,1 ;col8 = address 8 clrf _data call Load retlw 00 ;send 16 bits to 8x8 Module ;address 0 - 7 for columns ;and data for each column Load bcf gpio,2 ;open chip to receive address and data movlw 8 movwf serial ;load loop counter with 8 to transfer 8 bits movf address,w movwf temp3 rlf temp3,f ;move bit through carry rlf temp3,f ;move bit to bit0 position btfss temp3,0 ;these 3 instructions are very clever!!!! bcf gpio,1 ;to send LOW data bit btfsc temp3,0 ;see if the lowest bit is 0 or 1 bsf gpio,1 ;to send HIGH data bit rlf temp3,f ;put here to separate two gpio commands bsf gpio,4 ;clock HIGH call _12uS ;must have small delay between bsf and bcf bcf gpio,4 ;clock LOW to lock-in data bit decfsz serial,f goto $-9 ;send 8 bits DATA movlw 8 movwf serial ;load loop counter with 8 to transfer 8 bits rlf _data,f ;move bit 7 to bit 0 position rlf _data,f btfss _data,0 bcf gpio,1 ;to send LOW data bit btfsc _data,0 ;see if the lowest bit is 0 or 1 bsf gpio,1 ;to send HIGH data bit rlf _data,f ;put here to separate two gpio commands bsf gpio,4 ;clock HIGH call _12uS bcf gpio,4 ;clock LOW to lock-in data bit decfsz serial,f goto $-9 bsf gpio,2 ;close chip retlw 00 ;create non-shutdown mode noshutdown bcf gpio,2 ;open chip to receive address and data movlw 8 movwf serial ;load loop counter with 8 to transfer 8 bits movlw 0Ch ;0Ch accesses shutdown register movwf address rlf address,f ;move bit 7 to bit 0 position rlf address,f btfss address,0 ;these 3 instructions are very clever!!!! bcf gpio,1 ;to send LOW data bit btfsc address,0 ;see if the lowest bit is 0 or 1 bsf gpio,1 ;to send HIGH data bit rlf address,f ;put here to separate two gpio commands bsf gpio,4 ;clock HIGH call _12uS bcf gpio,4 ;clock LOW to lock-in data bit decfsz serial,f goto $-9 movlw 8 movwf serial ;load loop counter with 8 to transfer 8 bits movlw 7 ;1 needed in data register for normal operation movwf _data ; rlf _data,f ;move bit 7 to bit 0 position rlf _data,f btfss _data,0 bcf gpio,1 ;to send LOW data bit btfsc _data,0 ;see if the lowest bit is 0 or 1 bsf gpio,1 ;to send HIGH data bit rlf _data,f ;put here to separate two gpio commands bsf gpio,4 ;clock HIGH call _12uS bcf gpio,4 ;clock LOW to lock-in data bit decfsz serial,f goto $-9 bsf gpio,2 ;close chip retlw 00 ;Run - scrolls message across screen data held in 40h to 4Fh Run movlw 7Fh ;get number of letters from EEPROM 7Fh bsf status,rp0 ; select bank 1 movwf eeadr ; look at 7Fh bsf eecon1,rd ; initiate the read movf eedata,w ; put the read data into w bcf status,rp0 ; movwf letters ;letters holds the number of letters RunAA clrf current ;holds current EEPROM location RunA movf current,w ;first location in EEPROM bsf status,rp0 ; select bank 1 movwf eeadr ; look at 00h bsf eecon1,rd ; initiate the read movf eedata,w ; put the read data into w bcf status,rp0 ; movwf temp5 ;temp5 holds table jump value movf current,w ;end of message? xorwf letters,w btfsc status,z ;zero bit will be set if the same goto RunAA ;go to start of message movlw 6 movwf temp6 ;6 columns for each letter RunB movf temp5,w ;put jump-value into w call table1 movwf 48h ;put column-value into ghost column call Shift ;create "running effect" movlw 40h movwf 4 ;fsr for indirect addressing clrf address ;col1 = address 1 movlw 8 movwf columns ;load counter for 8 columns incf address,f ;for column 1 movf 0,w ;move data from file 40h into w movwf _data ;move data to _data file call Load incf 4,f ;increment FSR to look at file 41h decfsz columns,f goto $-6 call noshutdown ;tell8x8 to illuminate display call Scancols ;tell 8x8 to scan 8 columns call _100mS call _100mS incf temp5,f ;jump value for each letter decfsz temp6,f ;loop counter for 6 columns goto RunB incf current,f goto RunA ;scan all columns Scancols bcf gpio,2 ;open chip to receive address and data movlw 8 movwf serial ;load loop counter with 8 to transfer 8 bits movlw 0Bh ;0Bh accesses scan-limit register movwf temp4 rlf temp4,f ;move bit 7 to bit 0 position rlf temp4,f btfss temp4,0 ;these 3 instructions are very clever!!!! bcf gpio,1 ;to send LOW data bit btfsc temp4,0 ;see if the lowest bit is 0 or 1 bsf gpio,1 ;to send HIGH data bit rlf temp4,f ;put here to separate two gpio commands bsf gpio,4 ;clock HIGH call _12uS bcf gpio,4 ;clock LOW to lock-in data bit decfsz serial,f goto $-9 movlw 8 movwf serial ;load loop counter with 8 to transfer 8 bits movlw 7 ;7 is needed to scan 8 columns movwf temp4 rlf temp4,1 ;move bit 7 to bit 0 position rlf temp4,1 btfss temp4,0 bcf gpio,1 ;to send LOW data bit btfsc temp4,0 ;see if the lowest bit is 0 or 1 bsf gpio,1 ;to send HIGH data bit rlf temp4,f ;put here to separate two gpio commands bsf gpio,4 ;clock HIGH call _12uS bcf gpio,4 ;clock LOW to lock-in data bit decfsz serial,f goto $-9 bsf gpio,2 ;close chip retlw 00 ;shift columns to the LEFT also removes blank columns Shift movf 41h,w ;shift columns to the left movwf 40h movf 42h,w movwf 41h movf 43h,w movwf 42h movf 44h,w movwf 43h movf 45h,w movwf 44h movf 46h,w movwf 45h movf 47h,w movwf 46h movf 48h,w movwf 47h retlw 00 ;SwPressed sets bit 4, 3, 2, 1 in switch-flag SwPressed clrf Sw_Flag ;clear the switch flag bsf status, rp0 ;Bank 1 (see if switch is pressed) bcf TRISIO,5 ;clear bit GPIO,5 as output to charge cap. bcf status, rp0 ;bank 0 bsf gpio,5 ;make pin2 HIGH to charge cap. call _10mS ;charge cap bsf status, rp0 ;Bank 1 bsf TRISIO,5 ;set TRIS GP0,5 to detect discharged cap call _1mS ;create a delay to see if no sw pressed btfss gpio,5 goto $+3 bsf Sw_Flag,7 ;no switch pressed retlw 00 bsf status, rp0 ;Bank 1 bcf TRISIO,5 ;clear bit GPIO,5 as output to charge cap. bcf status, rp0 ;bank 0 bsf gpio,5 ;make pin2 HIGH to charge cap. call _10mS ;charge cap bsf status, rp0 ;Bank 1 bsf TRISIO,5 ;set TRIS GP0,5 to detect discharged cap bcf status, rp0 ;bank 0 call _12uS call _12uS call _12uS call _6uS btfsc gpio,5 goto $+3 bsf Sw_Flag,4 retlw 00 call _12uS btfsc gpio,5 goto $+3 bsf Sw_Flag,3 retlw 00 call _12uS call _6uS btfsc gpio,5 goto $+3 bsf Sw_Flag,2 retlw 00 call _12uS btfss gpio,5 bsf Sw_Flag,1 retlw 00 ;Sw3 = STORE - stores address of character (table1) into EEPROM ;eefile - total number of characters in EEPROM 217Fh ;eedata will be jump value ;eeadr will be zero at start-up Store ;look at 7Fh in EEPROM movlw 7Fh ;get location in EEPROM for storing next value bsf status,rp0 ; select bank 1 movwf eeadr ; look at 7Fh bsf eecon1,rd ; initiate the read movf eedata,w ; put the read data into w bcf status,rp0 ; movwf eefile ;and move to eefile movf eefile,w ;starts at 0 for EEPROM 1st location bsf status,rp0 ;select bank1 movwf eeadr bcf status,rp0 ;select bank0 call Dec_Jump movf jump,w ;dec jump 6 times to get start of letter bsf status,rp0 ;select bank1 movwf eedata bcf status,rp0 ;select bank0 call write incf eefile,f ;increment to store in next EEPROM location movlw 7Fh ;store in EEPROM last location bsf status,rp0 ;select bank1 movwf eeadr bcf status,rp0 ;select bank0 movf eefile,w ;store the number of letters bsf status,rp0 ;select bank1 movwf eedata bcf status,rp0 ;select bank0 call write retlw 00 write bsf status,rp0 ;select bank1 bsf eecon1,wren ;enable write movlw 55h ;unlock codes movwf eecon2 movlw 0aah movwf eecon2 bsf eecon1,wr ;write begins bcf status,rp0 ;select bank0 writeA btfss pir1,eeif ;wait for write to complete goto writeA bcf pir1,eeif bsf status,rp0 ;select bank1 bcf eecon1,wren ;disable other writes bcf status,rp0 ;select bank0 retlw 00 ;**************************************************************** ;* Main * ;**************************************************************** Main clrf Sw_Flag ;clear the switch flag call Display ;creates blank col1, ;data for cols:234567 and blank col8 call noshutdown call Scancols clrf Sw_Flag ;go to here for looping call SwPressed btfss Sw_Flag,7 ;see if no switch pressed goto $+2 ;sw pressed goto $-4 ;no sw pressed btfss Sw_Flag,1 ;see if "Forward" switch pressed goto $+7 ;see if other switch pressed Main1 call Display clrf Sw_Flag call SwPressed btfss Sw_Flag,7 ;see if no switch pressed goto $-3 goto $-.12 btfss Sw_Flag,2 ;see if "Back" switch pressed goto $+9 call Dec_Jump call Dec_Jump movlw 0FAh xorwf Jump,w btfss status,z ;zero bit will be set if the same goto $+3 movlw 0D2h ;address of last letter movwf jump ;go to bottom of table btfss Sw_Flag,3 ;see if "Store" switch pressed goto $+2 call Store btfss Sw_Flag,4 ;see if "Run" switch pressed goto Main1 call Run ;**************************************************************** ;*EEPROM Values to burn into EEPROM * ;**************************************************************** org 2100h ;org 2100h means the next byte of data will ;>be at location 00 in EEPROM de 00h ;de means Data EEPROM org 217Fh de 00h ;newly burnt chip: ;00 for number of char in EEPROM END

CASCADING THE 8x8
The next thing you can do with the 8x8 is cascade the modules to make it easier to read the running message.
We have developed a program to run 3 modules, however it will run 1,2 or 3 modules without any modification.
See the next page for the program:  CASCADING THE 8x8

ooo00000ooo
 

22-6-2013