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;SECTION NUMBER:
;
;GROUP MEMBER NAMES:
;1.
;2.
;3.
;4.
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;     Register Usage
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;  R0- x-cordinate for Draw_Block Trap
;  R1- y-cordinate for Draw_Block Trap
;  R2 - Global X-coordinate; start point for displaying characters - DONOT TAMPER for local use
;  R3 - Address in memory where bitmap for char is present
;  R4 
;  R5 
;  R6 
;  R7 - only store local values; You should be very careful when tampering with R7;
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;     Memory Locations being used
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;  SCROLL_LOOP_COUNTER: memory location for storing current value for scroll loop counter
;  COLUMN_LOOP_COUNTER: memory location for storing current value for column loop counter
;  ROW_LOOP_COUNTER: memory location for storing current value for row loop counter
;  BITMAP_A: Stores the address from where the bitmap of A starts (Look into hw6_bitmap.asm) 
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; Hints to get you started:
; look for TODOs corresponding to each task in the code and you need to fill in few instructions as per the comment
; Test after adding few lines of code and see if it behaves the you want it to
; You should be using lc3os_mod.asm as your OS
; You must load bitmap file as file before running the program
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;   program start
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    .ORIG x3000   ; Start program at x3000
START:    
    ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
    ; clear frame buffer on start
    ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
    
    ; R5 is the pointer to the where the pixels will be written to the display
    LD R5,VIDEO    
    ; Black pixel value
    LD R6,BLACK    
    ; The size of the entire frame buffer (We are going to write the value of BLACK in the entire frame buffer)
    LD R3,TOT_SIZE 
INIT_FRAME_LOOP:
    ;I repeat this same operation 8 times, that way we can speed up the overall loop 
    ;(8 writes/11 instructions instead of 1 write/4 instructions)
    STR R6,R5,#0    ; In this loop, we are storing the pixel in the appropriate location, then incrementing R5        
    STR R6,R5,#1        
    STR R6,R5,#2        
    STR R6,R5,#3        
    STR R6,R5,#4        
    STR R6,R5,#5        
    STR R6,R5,#6    
    STR R6,R5,#7    
    ADD R5,R5,#8     ;increment R5 by 8
    ADD R3,R3,#-8    ;subtracting 8 because this operation is done 8 times.
    BRp INIT_FRAME_LOOP        
        
    ; Initial start point -- GLOBAL X
    LD  R2, X_START           
    
    ; TODO initialize SCROLL_LOOP_COUNTER memory location to 10
    LD  R5, SCROLL_LOOP_COUNTER             
    ADD R5, R5, #10                         
    ST  R5, SCROLL_LOOP_COUNTER
    
SCROLL_LOOP:
    ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
    ; clear the display area
    ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
    LD R6,BLACK    ; Black pixel value
    LD R3,DISPSIZE ; The size of the entire frame buffer (We are going to write the value of BLACK in the entire frame buffer)
    
    LD R5, VIDEO    ; R5 is the pointer to the where the pixels will be written to the display
    LD R0, Y_START  ;
    LD R1, FOUR_ROW_WIDTH
    ; Loop for updating R5 to coordinate (0, Y_START)
SET_Y_OFFSET:    
    ADD R5, R5, R1  
    ADD R0, R0, #-1
    BRp SET_Y_OFFSET
    
    ; This loop is similar to init_frame_loop but clears only rows 6-13     
CLR_DISPLAY_LOOP0:
    STR R6,R5,#0    ;I repeat this same operation 8 times, that way we can speed up the overall loop (8 writes/18 instructions instead of 1 write/4 instructions)
    STR R6,R5,#1        
    STR R6,R5,#2        
    STR R6,R5,#3        
    STR R6,R5,#4        
    STR R6,R5,#5        
    STR R6,R5,#6    
    STR R6,R5,#7    
    ADD R5,R5,#8
    ADD R3,R3,#-8    ; Checking to see if the entire frame buffer has been written into
    BRp CLR_DISPLAY_LOOP0    ;subtracting 8 because this operation is done 8 times.
        

    ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
    ;   first char
    ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;       
    ; Update X for first character -- local X
    AND R0, R0, #0
    ADD R0, R2, #0 
    ; Update Y for first character
    LD  R1, Y_START
    ; Put the address of Bitmap for char to be drawn    
    LD  R3, BITMAP_CHAR_A    
    
    ; Load value BITMAP_WIDTH 
    LD R6, BITMAP_WIDTH                             
    ; initialize ROW_LOOP_COUNTER to BITMAP_WIDTH
    ST R6, ROW_LOOP_COUNTER
ROW_LOOP0:
    ; Load value BITMAP_WIDTH 
    LD  R4, BITMAP_WIDTH
    ; initialize COLUMN_LOOP_COUNTER to BITMAP_WIDTH
    ST  R4, COLUMN_LOOP_COUNTER
COLUMN_LOOP0:   
    ; TODO load the bitmap value to R4
    LDR R4, R3, #0 
    ; TODO (part 1): call conditional "TRAP 0x40" - dependent on value read into R4
    BRz SKIP_TRAP0
    TRAP x40
SKIP_TRAP0:
    ; TODO increment x
    ADD R0, R0, #1
    ; TODO increment R3 to go to next location which contains bitmap for next element    
    ADD R3, R3, #1                                
    ; TODO: Load COLUMN_LOOP_COUNTER value from memory                      
    LD  R4, COLUMN_LOOP_COUNTER         
    ; TODO: decrement loop count
    ADD R4, R4, #-1                          
    ; TODO: Update COLUMN_LOOP_COUNTER in memory
    ST  R4, COLUMN_LOOP_COUNTER
    ; TODO: branch to column loop if positive
    BRp COLUMN_LOOP0
                
    ; increment Y i.e. Y = Y + 1
    ADD R1, R1, #1
    ; decrement X by BITMAP_WIDTH i.e. X = X-7
    LD  R4, NEG_BITMAP_WIDTH     
    ADD R0, R0, R4      

    ; Load ROW_LOOP_COUNTER value from memory
    LD  R6, ROW_LOOP_COUNTER
    ; decrement the counter; counter = counter - 1
    ADD R6, R6, #-1            
    ; Store the updated value back into memory
    ST  R6, ROW_LOOP_COUNTER
    ; branch to column loop if positive
    BRp ROW_LOOP0
    ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
    ;   end of first char
    ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;    

    ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
    ;   second char
    ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;    
    ; TODO: Update X for next char - Add char length and little space
    LD  R4, BITMAP_WIDTH
    ADD R0, R0, R4          
    LD  R4, SPACE_BETWEEN_CHAR
    ADD R0, R0, R4          
    
    ; TODO: Update Y for next char
    LD  R1, Y_START         
    ; TODO: Update Bitmap Address for next char
    LD  R3, BITMAP_CHAR_B
    
    ; initialize row loop counter to BITMAP_WIDTH
    LD R6, BITMAP_WIDTH                             
    ST R6, ROW_LOOP_COUNTER
ROW_LOOP1:
    ; initialize column loop counter to BITMAP_WIDTH
    LD  R4, BITMAP_WIDTH
    ST  R4, COLUMN_LOOP_COUNTER
COLUMN_LOOP1:   
    ; load the bitmap value to R7
    LDR R4, R3, #0
    ; conditional TRAP to draw 
    BRz SKIP_TRAP1
    TRAP x40
SKIP_TRAP1:
    ; increment x
    ADD R0, R0, #1
    ; increment R3 to go to next location which contains bitmap for next element    
    ADD R3, R3, #1
    ; Load COLUMN_LOOP_COUNTER value from memory                      
    LD  R4, COLUMN_LOOP_COUNTER         
    ; decrement loop count
    ADD R4, R4, #-1                          
    ; Update COLUMN_LOOP_COUNTER in memory
    ST  R4, COLUMN_LOOP_COUNTER
    ; branch to column loop if positive
    BRp COLUMN_LOOP1        
    
    ; increment Y i.e. Y = Y + 1
    ADD R1, R1, #1
    ; decrement X by BITMAP_WIDTH i.e. X = X-7
    LD  R4, NEG_BITMAP_WIDTH     
    ADD R0, R0, R4      
    
    ; Load ROW_LOOP_COUNTER value from memory
    LD  R6, ROW_LOOP_COUNTER
    ; decrement the value by 1
    ADD R6, R6, #-1            
    ; Store into memory
    ST  R6, ROW_LOOP_COUNTER
    ; branch to row loop if positive
    BRp ROW_LOOP1
    ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
    ;   end of second char
    ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;    
            
    ; TODO: update GLOBAL X    
    ADD R2, R2, #-1

    ;;;; wait for some time
    LD  R0, SPIN_TIME    
SPIN0:
    ADD R0, R0, #-1
    BRp SPIN0      

    LD  R0, SPIN_TIME    
SPIN1:
    ADD R0, R0, #-1
    BRp SPIN1      
    
    ; TODO: Load value of SCROLL_LOOP_COUNTER from memory
    LD  R5, SCROLL_LOOP_COUNTER                        
    ; TODO Decrement the value by 1 
    ADD R5, R5, #-1 
    ; TODO Store the SCROLL_LOOP_COUNTER in memory           
    ST  R5, SCROLL_LOOP_COUNTER      
    ; TODO: Branch to SCROLL_LOOP if SCROLL_LOOP_COUNTER is positive
    BRp SCROLL_LOOP
    
    ; stop        
    HALT  

SPIN_TIME: .FILL 32767     

; start from row - 6 i.e. Y = 6                       
Y_START:            .FILL 6
; global start for X i.e. X = 1
X_START:            .FILL 1
; Space between 2 characters - 1 block
SPACE_BETWEEN_CHAR: .FILL 1
; Space taken by each character
CHAR_LEN:           .FILL 7
; Counter for SCROLL_LOOP
SCROLL_LOOP_COUNTER: .FILL 0
; Counter for COLUMN_LOOP
COLUMN_LOOP_COUNTER: .FILL 0
; Counter for ROW_LOOP
ROW_LOOP_COUNTER:   .FILL 0

; Start Address of Bitmap of A in memory
BITMAP_CHAR_A:      .FILL 0x5000

;; TODO: FILL IN ADDRESS for BITMAP_B here
BITMAP_CHAR_B:      .FILL 0x5031

;;; assuming 7x7 bitmap available row wise
BITMAP_WIDTH:       .FILL 7                  
NEG_BITMAP_WIDTH:   .FILL -7                  

VIDEO:              .FILL 0xC000
; color value for BLUE
COLOR:              .FILL 0x001F
; color value for BLACK
BLACK:              .FILL 0x0000
; color value for WHITE
WHITE:              .FILL 0xffff
DISPSIZE:           .FILL 0xE00
TOT_SIZE:           .FILL 0x3E00
ROW_WIDTH:          .FILL 0x80
FOUR_ROW_WIDTH:     .FILL 0x200        

;  Memory locations for register saving
DB_R0: .FILL 0x0
DB_R1: .FILL 0x0
DB_R2: .FILL 0x0
DB_R3: .FILL 0x0
DB_R4: .FILL 0x0
DB_R5: .FILL 0x0
DB_R6: .FILL 0x0
DB_R7: .FILL 0x0    


    .END