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Diffstat (limited to 'hacks/images/m6502/crunch6502.asm')
| -rw-r--r-- | hacks/images/m6502/crunch6502.asm | 292 |
1 files changed, 292 insertions, 0 deletions
diff --git a/hacks/images/m6502/crunch6502.asm b/hacks/images/m6502/crunch6502.asm new file mode 100644 index 0000000..56ea507 --- /dev/null +++ b/hacks/images/m6502/crunch6502.asm @@ -0,0 +1,292 @@ +;; Show "6502" on the screen waving up and down. +;; Jeremy English 29-December-2007 +;; +;; Each digit is stored as a pattern of vertical bits. +;; For example: +;; +;; 111111 This is the digit six. We think of the digit +;; 111111 by it's column pattern. The column patterns +;; 110000 are labeled at the bottom of the example. +;; 110000 Pattern B is 1100110011. The basic algorithm +;; 111111 is that we get the pattern, paint the first +;; 111111 bit (1 foreground, 0 background) then dec y +;; 110011 and get the next bit. +;; 110011 +;; 111111 The pattern for each digit is: +;; 111111 6 = AABBCC +;; ------ 5 = DDBBCC +;; AABBCC 0 = AAEEAA +;; 2 = CCBBDD + +;; Addresses $0 and $1 are used by the paint subroutine. +;; Addresses $2 through $6 are used by the display pattern subroutine +;; Address $7 is used in the main loop +;; Address $8 through $1a are used for the start positions +;; Address $1b is used by the display pattern subroutine +;; Address $1c is used as the color row offset. +;; Addresses $d0 through $ef store the font table + +jmp init_font_table +start: + +;; Initialize the pointers to the start position. +lda #<y_start_pos1 +sta $b +lda #>y_start_pos1 +sta $c +lda #<y_start_pos2 +sta $d +lda #>y_start_pos2 +sta $e +lda #<y_start_pos3 +sta $f +lda #>y_start_pos3 +sta $10 +lda #<y_start_pos4 +sta $11 +lda #>y_start_pos4 +sta $12 +lda #<y_start_pos5 +sta $13 +lda #>y_start_pos5 +sta $14 +lda #<y_start_pos4 +sta $15 +lda #>y_start_pos4 +sta $16 +lda #<y_start_pos3 +sta $17 +lda #>y_start_pos3 +sta $18 +lda #<y_start_pos2 +sta $19 +lda #>y_start_pos2 +sta $1a + + +lda #0 ; start position to use +sta $8 + +main_loop: +inc $1c ; increment the color offset. +inc $1d ; increment the starting x position +ldy $8 ; load the current start position index +ldx $b,y ; get the lsb from the table +txa +sta $9 ; store the msb of the start position pointer +iny ; move to the next position in the table +ldx $b,y ; get the msb from the table +txa +sta $a ; store the lsb of the start position pointer +iny ; move the index up by one +tya +cmp #$10 ; have we looked at all 16 start positions? +bne store_idx ; if not then keep the index and store it +lda #0 ; set the index back to zero +store_idx: +sta $8 ; save the index back in memory + +ldy #0 +lda #$ff +sta $4 ; initialize the column to FF +display_loop: + inc $4 ; increment the column + ldx $d0,y ; load the lsb from the font table + stx $2 + iny + ldx $d0,y ; load the msb from the font table + stx $3 + sty $7 ; save y in memory + jsr dis_pat ; Jump to the display pattern subroutine. + inc $4 ; increment the column + jsr dis_pat ; Each pattern gets painted twice so we have a thicker font + ldy $7 ; get y out of memory + iny ; increment the index + tya + cmp #$20 ; Did we display all of the columns? + bne display_loop ;if not continue +jmp main_loop +rts + +init_font_table: + ;;Setup a table in the zero page that contains the string "6502" + lda #<pattern_a ;start with digit 6. It's pattern is aabbcc + sta $d0 + lda #>pattern_a + sta $d1 + lda #<pattern_b + sta $d2 + lda #>pattern_b + sta $d3 + lda #<pattern_c + sta $d4 + lda #>pattern_c + sta $d5 + lda #<pattern_null ;We want to space everything out with blanks + sta $d6 + lda #>pattern_null + sta $d7 + lda #<pattern_d ;load memory for digit 5 ddbbcc + sta $d8 + lda #>pattern_d + sta $d9 + lda #<pattern_b + sta $da + lda #>pattern_b + sta $db + lda #<pattern_c + sta $dc + lda #>pattern_c + sta $dd + lda #<pattern_null + sta $de + lda #>pattern_null + sta $df + lda #<pattern_a ;load memory for digit 0 aaeeaa + sta $e0 + lda #>pattern_a + sta $e1 + lda #<pattern_e + sta $e2 + lda #>pattern_e + sta $e3 + lda #<pattern_a + sta $e4 + lda #>pattern_a + sta $e5 + lda #<pattern_null + sta $e6 + lda #>pattern_null + sta $e7 + lda #<pattern_c ;load memory for digit 2 ccbbdd + sta $e8 + lda #>pattern_c + sta $e9 + lda #<pattern_b + sta $ea + lda #>pattern_b + sta $eb + lda #<pattern_d + sta $ec + lda #>pattern_d + sta $ed + lda #<pattern_null + sta $ee + lda #>pattern_null + sta $ef + jmp start + + +;; Display a pattern on the screen. The pattern to use is +;; stored at $2 and $3. The current column is stored at $4. +dis_pat: + ldy $4 ; Load the current column into y + lda ($9),y ; Get the start position for y + tay + sty $5 ; Store the starting position in memory + ldy #0 ; We have 12 bits that need to be painted +dis_pat_loop: + lda ($2),y ; get a bit from the pattern + pha ; save the color on the stack + tya ; move the index into the accumulator + clc ; clear the carry + adc $5 ; add the starting position to the index + sty $6 ; store the index + tay ; The calculated y position + ldx $4 ; The x position is the current column + pla ; pop the color off of the stack + beq go_paint ; black just paint it + clc ; get rid of any carry bit + sty $1b ; save the y coordinate + tya + clc + adc $1c ; add the color offset + and #$7 ; make sure the look up is in range + tay ; move the new index into y so we can look up the color + lda color_row,y ; if not black get the row color + ldy $1b ; restore the y coordinate +go_paint: + jsr paint ; paint the pixel on the screen + ldy $6 ; get the index out of memory + iny ; increment the index + tya + cmp #12 ; Have we looked at all of the bits? + bne dis_pat_loop ; if not then continue looking + rts ; else return from the subroutine + +;; Paint - Put a pixel on the screen by using the x registry for +;; the x position, the y registry for the y position and +;; the accumulator for the color. +paint: + pha ; Save the color + lda yl,y ; Get the LSB of the memory address for y + sta $0 ; Store it first + lda yh,y ; Get the MSB of the memory address for y + sta $1 ; Store it next + txa ; We want x in the y registry so we transfer it to A + tay ; and then A into y. + pla ; Pop the color off of the stack + sta ($0),y ; Store the color at the correct y + x address. + rts ; return from the subroutine. + +;; Paint uses the following two tables to look up the +;; correct address for a y coordinate between +;; 0 and 31. + +;; Y cord MSB +yh: + dcb $02, $02, $02, $02, $02, $02, $02, $02 + dcb $03, $03, $03, $03, $03, $03, $03, $03 + dcb $04, $04, $04, $04, $04, $04, $04, $04 + dcb $05, $05, $05, $05, $05, $05, $05, $05 +;; Y cord LSB +yl: + dcb $00, $20, $40, $60, $80, $a0, $c0, $e0 + dcb $00, $20, $40, $60, $80, $a0, $c0, $e0 + dcb $00, $20, $40, $60, $80, $a0, $c0, $e0 + dcb $00, $20, $40, $60, $80, $a0, $c0, $e0 + +;; A zero is on the end of each pattern to clean up +;; residue left by waving. +pattern_a: + dcb 0,1,1,1,1,1,1,1,1,1,1,0 + +pattern_b: + dcb 0,1,1,0,0,1,1,0,0,1,1,0 + +pattern_c: + dcb 0,1,1,0,0,1,1,1,1,1,1,0 + +pattern_d: + dcb 0,1,1,1,1,1,1,0,0,1,1,0 + +pattern_e: + dcb 0,1,1,0,0,0,0,0,0,1,1,0 + +pattern_null: + dcb 0,0,0,0,0,0,0,0,0,0,0,0 + +;; Table that store the current start position +;; of each y column. +y_start_pos1: + dcb 10,10,9,9,8,8,7,7,6,6,7,7,8,8,9,9,10,10,9,9,8,8,7,7 + dcb 6,6,7,7,8,8 + +y_start_pos2: + dcb 9,9,8,8,8,8,8,8,7,7,8,8,8,8,8,8,9,9,8,8,8,8,8,8 + dcb 7,7,8,8,8,8 + +y_start_pos3: + dcb 8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8 + dcb 8,8,8,8,8,8 + +y_start_pos4: + dcb 7,7,8,8,8,8,8,8,9,9,8,8,8,8,8,8,7,7,8,8,8,8,8,8 + dcb 9,9,8,8,8,8 + +y_start_pos5: + dcb 6, 6,7,7,8,8,9,9,10,10,9,9,8,8,7,7, 6, 6,7,7,8,8,9,9 + dcb 10,10,9,9,8,8 + +color_row: + dcb $7,$8,$9,$2,$4,$6,$e,$3,$d,$5 |