LIST p=16f648a ; tell assembler what chip we are using include "P16f648a.inc" ; include the defaults for the chip __config 0x3f18 ; sets the configuration settings (oscillator type etc.) PC equ h'02' ; The program counter will be refered to as PC cblock h'20' ; start of general purpose registers - this is where we start defining variable names counta ; used in the delay routines countb ; used in the delay routines vram_1 ; a video ram location vram_2 ; a video ram location vram_3 ; a video ram location vram_4 ; a video ram location vram_5 ; a video ram location vram_6 ; a video ram location vram_7 ; a video ram location vram_8 ; a video ram location vtemp_1 ; a temporary video ram location (used when tranfering vram data to the next vram location) vtemp_2 ; a temporary video ram location (used when tranfering vram data to the next vram location) vtemp_3 ; a temporary video ram location (used when tranfering vram data to the next vram location) vtemp_4 ; a temporary video ram location (used when tranfering vram data to the next vram location) vtemp_5 ; a temporary video ram location (used when tranfering vram data to the next vram location) vtemp_6 ; a temporary video ram location (used when tranfering vram data to the next vram location) vtemp_7 ; a temporary video ram location (used when tranfering vram data to the next vram location) ship_data pc_data ; used in the display data program counter repeat_frame ; used to determine how many times we will be repeating each 'frame' button_timer ; used to help in slowing down the button repeat rate (it prevents the car from moving many times for one button press) button_adjust ; used to help in slowing down the button repeat rate (it prevents the car from moving many times for one button press) stop_repeat ; used to help in slowing down the button repeat rate (it prevents the car from moving many times for one button press) speed laser_x laser_y shot_fired laser_timer laser_distance top_alien_data middle_alien_data bottom_alien_data temp_ram move_timer direction move_down_timer top_alien_line middle_alien_line bottom_alien_line line_map lost_life level_up anim_repeat current_level shield end_timer UFO do_UFO UFO_speed endc org h'0000' ; org sets the origin, 0x0000 for the 16F628, movlw h'07' movwf CMCON ; turn comparators off (make it like a 16F84) bsf STATUS, RP0 ; select bank 1 movlw b'00000000' ; set PORTB all outputs movwf TRISB ; movlw b'00100000' ; set PORTA all outputs except for bit 5 movwf TRISA ; bcf STATUS, RP0 ; select bank 0 goto setup advance_level_data incf pc_data, 1 ; increment pc_data by one and then movf pc_data, w ; move it into our working register THEN addwf PC ; add this number to our program counter nop ; skip one step... retlw b'00100100' retlw b'00000010' retlw b'01001000' retlw b'00000000' retlw b'00100000' retlw b'01000000' retlw b'00000010' retlw b'00001000' retlw b'01000010' retlw b'00000001' retlw b'01000000' retlw b'00000000' retlw b'01000100' retlw b'10000000' retlw b'00100001' movlw d'01' ; and now reset our pc_data variable so that we can movwf pc_data ; draw the track again from the start retlw b'00100100' setup ; Okay, lets get everything setup, ready to play the game! clrf shot_fired clrf laser_x movlw d'07' movwf laser_distance movlw b'00000010' movwf laser_y movlw b'11011010' ; This basically disables all 74373 outputs, and closes movwf PORTA ; all 74373 latches. clrf stop_repeat ; clear all 8 bits in stop repeat (even though we only use two.) movlw b'00010000' ; set the start position of our car movwf ship_data ; (almost in the middle of the screen) movlw d'08' ; set our button repsonse delay (the higher the number, movwf button_adjust ; the longer you have to wait to be able to push the button again) movlw d'25' movwf laser_timer movlw d'30' movwf UFO_speed clrf do_UFO movlw b'10000000' movwf UFO movlw d'50' movwf end_timer clrf lost_life movlw b'00000001' movwf current_level movlw d'255' movwf move_down_timer movlw b'00010101' movwf direction movlw d'120' movwf move_timer movlw d'16' ; set our button repsonse delay (the higher the number, movwf button_adjust next_level movlw b'01011010' movwf shield clrf temp_ram movlw b'01111110' movwf top_alien_data movwf middle_alien_data movwf bottom_alien_data movlw b'00000001' movwf line_map movlw b'01000000' movwf top_alien_line movlw b'00100000' movwf middle_alien_line movlw b'00010000' movwf bottom_alien_line clrf level_up clrf vram_1 ; these next lines clear our video ram. clrf vram_2 ; if we didnt clear them, then we would get random clrf vram_3 ; dots on our screen and would more than likely crash clrf vram_4 ; as soon as we started playing! (experiment with not clrf vram_5 ; clearing all these vrams and see what happens!) clrf vram_6 ; .... clrf vram_7 ; .... clrf vram_8 ; .... begin call ship ; call the display routine call draw_UFO call shields call laser call draw_aliens call hit_aliens continue call check_aliens btfss lost_life, 0 call move_aliens call game_status btfsc level_up, 0 call level_anim btfsc lost_life, 0 goto hold_end goto begin goto next_level ; do it all again! hold_end call long_delay btfsc lost_life, 0 decfsz end_timer, f goto begin goto setup ship btfsc stop_repeat, 1 call button_time call joystick ; First of all, call the joystick to see if we're moving. movf ship_data, w ; Copy the contents of car_data to the w register, movwf PORTB ; then copy this data from w to PORTB. bsf PORTA, 4 ; open the COLUMN data latch to allow the 8 bits to go through bcf PORTA, 4 ; now close the latch and this will hold the 8 bits on the 74373 output. movlw b'00000001' ; now copy these 8 bits to the w register movwf PORTB ; and then from the w register to PORTB bsf PORTA, 0 ; Now open the 74373 latches connected to the red LEDs bcf PORTA, 0 ; then close the latches and now we hold onto that data. bcf PORTA, 1 ; enable the red LEDs 74373 output and also bcf PORTA, 6 ; enable the COLUMN 74373 output (this will output all that data to the screen) call delay ; call the delay - this will hold that info on the screen for a split second, bsf PORTA, 1 ; then when the delay is finished, disable both 74373 outputs bsf PORTA, 6 ; which will turn off those leds. return ; now were finished, return to the main program draw_UFO btfss do_UFO, 0 return movlw b'10000000' movwf PORTB bsf PORTA, 0 bcf PORTA, 0 movf UFO, w movwf PORTB bsf PORTA, 4 bcf PORTA, 4 bcf PORTA, 1 bcf PORTA, 6 call delay bsf PORTA, 1 bsf PORTA, 6 decfsz UFO_speed, f return bcf STATUS, C rrf UFO, f movlw d'30' movwf UFO_speed btfss STATUS, C return bcf do_UFO, 0 movlw b'10000000' movwf UFO return shields movlw b'00000010' movwf PORTB bsf PORTA, 2 bcf PORTA, 2 movf shield, w movwf PORTB bsf PORTA, 4 bcf PORTA, 4 bcf PORTA, 3 bcf PORTA, 6 call delay bsf PORTA, 3 bsf PORTA, 6 return laser btfss shot_fired, 0 ; check to see if a shot has been fired return ; if not, then just return movf laser_x, w movwf PORTB bsf PORTA, 4 bcf PORTA, 4 movf laser_y, w movwf PORTB bsf PORTA, 2 bcf PORTA, 2 bcf PORTA, 3 bcf PORTA, 6 call delay bsf PORTA, 3 bsf PORTA, 6 decfsz laser_timer, f return bcf STATUS, C rlf laser_y, f movlw d'25' movwf laser_timer decfsz laser_distance, f return reset_shot movlw b'00000010' movwf laser_y movlw d'07' movwf laser_distance bcf shot_fired, 0 return draw_aliens movf top_alien_line, w movwf PORTB bsf PORTA, 0 bcf PORTA, 0 movf top_alien_data, w movwf PORTB bsf PORTA, 4 bcf PORTA, 4 bcf PORTA, 1 bcf PORTA, 6 call delay bsf PORTA, 1 bsf PORTA, 6 movf middle_alien_line, w movwf PORTB bsf PORTA, 2 bcf PORTA, 2 movf middle_alien_data, w movwf PORTB bsf PORTA, 4 bcf PORTA, 4 bcf PORTA, 3 bcf PORTA, 6 call delay bsf PORTA, 3 bsf PORTA, 6 movf bottom_alien_line, w movwf PORTB bsf PORTA, 0 bcf PORTA, 0 bsf PORTA, 2 bcf PORTA, 2 movf bottom_alien_data, w movwf PORTB bsf PORTA, 4 bcf PORTA, 4 bcf PORTA, 1 bcf PORTA, 3 bcf PORTA, 6 call delay bsf PORTA, 1 bsf PORTA, 3 bsf PORTA, 6 return alien_line_change decfsz move_down_timer, f return bsf do_UFO, 0 bcf STATUS, C rlf line_map, f rrf top_alien_line, f rrf middle_alien_line, f rrf bottom_alien_line, f btfsc current_level, 0 movlw d'255' btfsc current_level, 1 movlw d'225' btfsc current_level, 2 movlw d'200' btfsc current_level, 3 movlw d'180' btfsc current_level, 4 movlw d'155' btfsc current_level, 5 movlw d'120' btfsc current_level, 6 movlw d'100' btfsc current_level, 7 movlw d'80' movwf move_down_timer return hit_aliens btfss laser_y, 7 goto skip_UFO movf laser_x,w andwf UFO, w xorwf UFO, f skip_UFO movf laser_x, w andwf shield, w xorwf shield, f btfsc line_map, 0 call map_0 btfsc line_map, 1 call map_1 btfsc line_map, 2 call map_2 btfsc line_map, 3 call map_3 btfsc line_map, 4 call map_4 btfsc line_map, 5 call map_5 btfsc line_map, 6 call map_6 goto continue map_0 btfss shot_fired, 0 return btfsc laser_y, 4 call hit_bottom btfsc laser_y, 5 call hit_middle btfsc laser_y, 6 call hit_top goto continue map_1 btfss shot_fired, 0 return btfsc laser_y, 3 call hit_bottom btfsc laser_y, 4 call hit_middle btfsc laser_y, 5 call hit_top goto continue map_2 btfss shot_fired, 0 return btfsc laser_y, 2 call hit_bottom btfsc laser_y, 3 call hit_middle btfsc laser_y, 4 call hit_top goto continue map_3 btfss shot_fired, 0 return btfsc laser_y, 1 call hit_bottom btfsc laser_y, 2 call hit_middle btfsc laser_y, 3 call hit_top goto continue map_4 movf ship_data, w andwf bottom_alien_data, w btfss STATUS, Z bsf lost_life, 0 btfss shot_fired, 0 return btfsc laser_y, 0 call hit_bottom btfsc laser_y, 1 call hit_middle btfsc laser_y, 2 call hit_top goto continue map_5 movf ship_data, w andwf middle_alien_data, w btfss STATUS, Z bsf lost_life, 0 btfss shot_fired, 0 return btfsc laser_y, 0 call hit_middle btfsc laser_y, 1 call hit_top goto continue map_6 movf ship_data, w andwf top_alien_data, w btfss STATUS, Z bsf lost_life, 0 btfss shot_fired, 0 return btfsc laser_y, 0 call hit_top goto continue hit_bottom movf laser_x, w andwf bottom_alien_data, w ; first we and the answer to see if anything will get removed or not. movwf temp_ram btfss STATUS, Z call reset_shot movf temp_ram, w xorwf bottom_alien_data, f goto continue hit_middle movf laser_x, w andwf middle_alien_data, w ; first we and the answer to see if anything will get removed or not. movwf temp_ram btfss STATUS, Z call reset_shot movf temp_ram, w xorwf middle_alien_data, f goto continue hit_top movf laser_x, w andwf top_alien_data, w ; first we and the answer to see if anything will get removed or not. movwf temp_ram btfss STATUS, Z call reset_shot movf temp_ram, w xorwf top_alien_data, f goto continue check_aliens btfsc top_alien_data, 0 call top_go_left btfsc top_alien_data, 7 call top_go_right btfsc middle_alien_data, 0 call middle_go_left btfsc middle_alien_data, 7 call middle_go_right btfsc bottom_alien_data, 0 call bottom_go_left btfsc bottom_alien_data, 7 call bottom_go_right return top_go_left call alien_line_change bcf direction, 1 bsf direction, 0 return top_go_right bcf direction, 0 bsf direction, 1 return middle_go_left bcf direction, 3 bsf direction, 2 return middle_go_right bcf direction, 2 bsf direction, 3 return bottom_go_left bcf direction, 5 bsf direction, 4 return bottom_go_right bcf direction, 4 bsf direction, 5 return move_aliens decfsz move_timer, f return bcf STATUS, C btfsc direction, 0 rlf top_alien_data, f btfsc direction, 1 rrf top_alien_data, f btfsc direction, 2 rlf middle_alien_data, f btfsc direction, 3 rrf middle_alien_data, f btfsc direction, 4 rlf bottom_alien_data, f btfsc direction, 5 rrf bottom_alien_data, f btfsc current_level, 0 movlw d'120' btfsc current_level, 1 movlw d'20' btfsc current_level, 2 movlw d'100' btfsc current_level, 3 movlw d'90' btfsc current_level, 4 movlw d'80' btfsc current_level, 5 movlw d'70' btfsc current_level, 6 movlw d'60' btfsc current_level, 7 movlw d'50' movwf move_timer return game_status movf top_alien_data, w iorwf middle_alien_data, w iorwf bottom_alien_data, w btfss STATUS, Z return bsf level_up, 0 rlf current_level, f return joystick call port_b_input ; First we need to make PORTB an input before we can check anything. bcf PORTA, 7 ; Now we need to enable the 74373 connected to all the buttons btfss PORTB, 2 ; Check the left button. if it is a 0 (which means it's pressed) call go_left ; then call the go_left routine, if its a 1 then jump to the next line. btfss PORTB, 3 ; Check the right button. if it is a 0 (which means it's pressed) call go_right ; then call the go_right routine, if its a 1 then jump to the next line. btfss PORTB, 5 ; Check the 'B' button, if it is a 0 (which means it's pressed) call shoot ; then call the go_right routine, if its a 1 then jump to the next line. btfss PORTB, 6 ; Check the 'Reset' button, if it is a 0 (which means it's pressed) goto setup ; Then goto setup (reset the game) if its a 1, then jump to the next line. bsf PORTA, 7 ; disable the 74373 connected to the buttons. call port_b_output ; make PORTB an output again return ; and finally, return back to the main program! port_b_input ; This routine makes all of PORTB into inputs bsf STATUS, RP0 ; which allows us to then read from the movlw b'11111111' ; Joystick. movwf TRISB ; bcf STATUS, RP0 ; return ; Now return to where we can from... port_b_output ; This routine makes all of PORTB outputs again bsf STATUS, RP0 ; If we didnt make PORTB an output again, then movlw b'00000000' ; we could never display any data on our screen! movwf TRISB ; bcf STATUS, RP0 ; return ; Now return to where we can from... go_left btfsc ship_data, 0 return btfsc stop_repeat, 0 ; First we check if the stop_repeat bit is set return bcf STATUS, C ; THIS ENSURES THAT YOU DON'T GET EXTRA SHIPS COMING IN! rrf ship_data, 1 ; If it is not set then the car will move across one space. bsf stop_repeat, 1 ; Now that we have moved one space we want to prevent our bsf stop_repeat, 0 ; car from moving another space straight away. so we set movf button_adjust, w ; the stop_repeat bits which will remain set untill the movwf button_timer ; specified time period is complete. Without this, the car return ; would move way to fast for us to be able to play the game go_right btfsc ship_data, 7 return btfsc stop_repeat, 0 ; First we check if the stop_repeat bit is set return bcf STATUS, C ; THIS ENSURES THAT YOU DON'T GET EXTRA SHIPS COMING IN! rlf ship_data, 1 ; If it is not set then the car will move across one space. bsf stop_repeat, 1 ; Now that we have moved one space we want to prevent our bsf stop_repeat, 0 ; car from moving another space straight away. so we set movf button_adjust, w ; the stop_repeat bits which will remain set untill the movwf button_timer ; specified time period is complete. Without this, the car return ; would move way to fast for us to be able to play the game shoot btfsc shot_fired, 0 return call reset_shot bsf shot_fired, 0 movf ship_data, w movwf laser_x return button_time ; This routine decrements the button_timer by one decfsz button_timer, 1 ; (we can change the value of button_timer in the setup routine) return ; If the timer has not yet reached zero, then it returns to the main program bcf stop_repeat ,0 ; If the timer has reached zero, then we clear the stop_repeat bits bcf stop_repeat, 1 ; this then allows us to press a button again! return ; Now return to where we can from... level_anim movlw d'100' movwf anim_repeat next_frame call fill_vram movlw d'04' movwf repeat_frame ; so we grab that data from speed and copy it to our frame_rate loop movf vram_1, w ; Now we grab the first COLUMN of data from vram_1. movwf PORTB ; then we copy it to PORTB bsf PORTA, 4 ; now that its in PORTB we need to latch it to the COLUMN memory. bcf PORTA, 4 ; so the latch was opened, now we need to close it (the data will now stay there) movlw b'10000000' ; This now activates the top row of cathodes by moving movwf PORTB ; '10000000' to PORTB, bsf PORTA, 2 ; then latching it onto the green data latch bcf PORTA, 2 ; then closing the latch (the data is now held there) bcf PORTA, 6 ; Now that all our data is ready, we can enable our 74373 outputs. bcf PORTA, 3 ; PORTA, 6 is the COLUMN data enable - PORTA, 3 is the green data enable call delay ; Call the delay (to hold that one row ON for a split second) bsf PORTA, 6 ; Now disable both outputs (remember PORTA, 6 is the COLUMN data bsf PORTA, 3 ; and PORTA, 3 is the green data) movf vram_2, w ; Now we grab the second COLUMN of data from vram_2. movwf PORTB ; then we copy it to PORTB bsf PORTA, 4 ; now that its in PORTB we need to latch it to the COLUMN memory. bcf PORTA, 4 ; so the latch was opened, now we need to close it (the data will now stay there) movlw b'01000000' ; This now activates the top row of cathodes by moving movwf PORTB ; '01000000' to PORTB, bsf PORTA, 2 ; then latching it onto the green data latch bcf PORTA, 2 ; then closing the latch (the data is now held there) bcf PORTA, 6 ; Now that all our data is ready, we can enable our 74373 outputs. bcf PORTA, 3 ; PORTA, 6 is the COLUMN data enable - PORTA, 3 is the green data enable call delay ; Call the delay (to hold that one row ON for a split second) bsf PORTA, 6 ; Now disable both outputs (remember PORTA, 6 is the COLUMN data bsf PORTA, 3 ; and PORTA, 3 is the green data) movf vram_3, w ; Now we grab the third COLUMN of data from vram_3. movwf PORTB ; then we copy it to PORTB bsf PORTA, 4 ; now that its in PORTB we need to latch it to the COLUMN memory. bcf PORTA, 4 ; so the latch was opened, now we need to close it (the data will now stay there) movlw b'00100000' ; This now activates the top row of cathodes by moving movwf PORTB ; '00100000' to PORTB, bsf PORTA, 2 ; then latching it onto the green data latch bcf PORTA, 2 ; then closing the latch (the data is now held there) bcf PORTA, 6 ; Now that all our data is ready, we can enable our 74373 outputs. bcf PORTA, 3 ; PORTA, 6 is the COLUMN data enable - PORTA, 3 is the green data enable call delay ; Call the delay (to hold that one row ON for a split second) bsf PORTA, 6 ; Now disable both outputs (remember PORTA, 6 is the COLUMN data bsf PORTA, 3 ; and PORTA, 3 is the green data) movf vram_4, w ; Now we grab the fourth COLUMN of data from vram_4. movwf PORTB ; then we copy it to PORTB bsf PORTA, 4 ; now that its in PORTB we need to latch it to the COLUMN memory. bcf PORTA, 4 ; so the latch was opened, now we need to close it (the data will now stay there) movlw b'00010000' ; This now activates the top row of cathodes by moving movwf PORTB ; '00010000' to PORTB, bsf PORTA, 2 ; then latching it onto the green data latch bcf PORTA, 2 ; then closing the latch (the data is now held there) bcf PORTA, 6 ; Now that all our data is ready, we can enable our 74373 outputs. bcf PORTA, 3 ; PORTA, 6 is the COLUMN data enable - PORTA, 3 is the green data enable call delay ; Call the delay (to hold that one row ON for a split second) bsf PORTA, 6 ; Now disable both outputs (remember PORTA, 6 is the COLUMN data bsf PORTA, 3 ; and PORTA, 3 is the green data) movf vram_5, w ; Now we grab the fifth COLUMN of data from vram_5. movwf PORTB ; then we copy it to PORTB bsf PORTA, 4 ; now that its in PORTB we need to latch it to the COLUMN memory. bcf PORTA, 4 ; so the latch was opened, now we need to close it (the data will now stay there) movlw b'00001000' ; This now activates the top row of cathodes by moving movwf PORTB ; '00001000' to PORTB, bsf PORTA, 2 ; then latching it onto the green data latch bcf PORTA, 2 ; then closing the latch (the data is now held there) bcf PORTA, 6 ; Now that all our data is ready, we can enable our 74373 outputs. bcf PORTA, 3 ; PORTA, 6 is the COLUMN data enable - PORTA, 3 is the green data enable call delay ; Call the delay (to hold that one row ON for a split second) bsf PORTA, 6 ; Now disable both outputs (remember PORTA, 6 is the COLUMN data bsf PORTA, 3 ; and PORTA, 3 is the green data) movf vram_6, w ; Now we grab the sixth COLUMN of data from vram_6. movwf PORTB ; then we copy it to PORTB bsf PORTA, 4 ; now that its in PORTB we need to latch it to the COLUMN memory. bcf PORTA, 4 ; so the latch was opened, now we need to close it (the data will now stay there) movlw b'00000100' ; This now activates the top row of cathodes by moving movwf PORTB ; '00000100' to PORTB, bsf PORTA, 2 ; then latching it onto the green data latch bcf PORTA, 2 ; then closing the latch (the data is now held there) bcf PORTA, 6 ; Now that all our data is ready, we can enable our 74373 outputs. bcf PORTA, 3 ; PORTA, 6 is the COLUMN data enable - PORTA, 3 is the green data enable call delay ; Call the delay (to hold that one row ON for a split second) bsf PORTA, 6 ; Now disable both outputs (remember PORTA, 6 is the COLUMN data bsf PORTA, 3 ; and PORTA, 3 is the green data) movf vram_7, w ; Now we grab the seventh COLUMN of data from vram_7. movwf PORTB ; then we copy it to PORTB bsf PORTA, 4 ; now that its in PORTB we need to latch it to the COLUMN memory. bcf PORTA, 4 ; so the latch was opened, now we need to close it (the data will now stay there) movlw b'00000010' ; This now activates the top row of cathodes by moving movwf PORTB ; '00000010' to PORTB, bsf PORTA, 2 ; then latching it onto the green data latch bcf PORTA, 2 ; then closing the latch (the data is now held there) bcf PORTA, 6 ; Now that all our data is ready, we can enable our 74373 outputs. bcf PORTA, 3 ; PORTA, 6 is the COLUMN data enable - PORTA, 3 is the green data enable call delay ; Call the delay (to hold that one row ON for a split second) bsf PORTA, 6 ; Now disable both outputs (remember PORTA, 6 is the COLUMN data bsf PORTA, 3 ; and PORTA, 3 is the green data) movf vram_8, w ; Now we grab the eigth COLUMN of data from vram_8. movwf PORTB ; then we copy it to PORTB bsf PORTA, 4 ; now that its in PORTB we need to latch it to the COLUMN memory. bcf PORTA, 4 ; so the latch was opened, now we need to close it (the data will now stay there) movlw b'00000001' ; This now activates the top row of cathodes by moving movwf PORTB ; '00000001' to PORTB, bsf PORTA, 2 ; then latching it onto the green data latch bcf PORTA, 2 ; then closing the latch (the data is now held there) bcf PORTA, 6 ; Now that all our data is ready, we can enable our 74373 outputs. bcf PORTA, 3 ; PORTA, 6 is the COLUMN data enable - PORTA, 3 is the green data enable call delay ; Call the delay (to hold that one row ON for a split second) bsf PORTA, 6 ; Now disable both outputs (remember PORTA, 6 is the COLUMN data bsf PORTA, 3 ; and PORTA, 3 is the green data) decfsz repeat_frame, f ; then decrease repeat_frame by one, goto loop decfsz anim_repeat, f goto next_frame goto setup fill_vram movf vram_1, 0 ; Copy vram_1 into vtemp_1 to use as a backup movwf vtemp_1 ; storage location. (just before we overwrite vram_1) movf vram_2, 0 ; Copy vram_1 into vtemp_2 to use as a backup movwf vtemp_2 ; storage location. (just before we overwrite vram_2) movf vram_3, 0 ; Copy vram_1 into vtemp_3 to use as a backup movwf vtemp_3 ; storage location. (just before we overwrite vram_3) movf vram_4, 0 ; Copy vram_1 into vtemp_4 to use as a backup movwf vtemp_4 ; storage location. (just before we overwrite vram_4) movf vram_5, 0 ; Copy vram_1 into vtemp_5 to use as a backup movwf vtemp_5 ; storage location. (just before we overwrite vram_5) movf vram_6, 0 ; Copy vram_1 into vtemp_6 to use as a backup movwf vtemp_6 ; storage location. (just before we overwrite vram_6) movf vram_7, 0 ; Copy vram_7 into vtemp_7 to use as a backup movwf vtemp_7 ; storage location. (just before we overwrite vram_7) call advance_level_data ; Call track_data routine and return with a byte of data in the w register movwf vram_1 ; then copy the new byte of data to the first vram location movf vtemp_1, 0 ; copy what was in vram_1 into vram_2 (remember how we made movwf vram_2 ; a backup of vram_1 and called it vtemp_1.) movf vtemp_2, 0 ; copy what was in vram_2 into vram_3 (remember how we made movwf vram_3 ; a backup of vram_2 and called it vtemp_2.) movf vtemp_3, 0 ; copy what was in vram_3 into vram_4 (remember how we made movwf vram_4 ; a backup of vram_3 and called it vtemp_3.) movf vtemp_4, 0 ; copy what was in vram_4 into vram_5 (remember how we made movwf vram_5 ; a backup of vram_4 and called it vtemp_4.) movf vtemp_5, 0 ; copy what was in vram_5 into vram_6 (remember how we made movwf vram_6 ; a backup of vram_5 and called it vtemp_5.) movf vtemp_6, 0 ; copy what was in vram_6 into vram_7 (remember how we made movwf vram_7 ; a backup of vram_6 and called it vtemp_6.) movf vtemp_7, 0 ; copy what was in vram_7 into vram_8 (remember how we made movwf vram_8 ; a backup of vram_7 and called it vtemp_7.) return delay ; This first delay is a rather fast one. movlw d'03' ; You can make the delay longer by movwf counta ; increasing the decimal value. Or you movwf countb ; can make the delay shorter by decreasing again decfsz counta, 1 ; the decimal value. goto again ; decfsz countb, 1 ; goto again ; once counta and countb have reached zero return ; it will return to the main program long_delay ; This first delay is a rather fast one. movlw d'100' ; You can make the delay longer by movwf counta ; increasing the decimal value. Or you movwf countb ; can make the delay shorter by decreasing again_long decfsz counta, 1 ; the decimal value. goto again_long ; decfsz countb, 1 ; goto again_long ; once counta and countb have reached zero return ; it will return to the main program end ; That's it!