This idea sort of arose from some code I wrote for another topic (viewtopic.php?f=10&t=10135#p113451), for using the 4x4 pixel "chunky" PETSCII bitmap.
It can be used to list programs (SYS6144:LIST) and stuff, because it scrolls the screen. (Note: This newer version sets color):
Code: Select all
; Five Column Mode
; Usage
; jsr Init5x5 ; Set up 5 column mode, reset to top left
; lda #"*" ; Normal invocation of
; jsr $ffd2 ; CHROUT
; Or...
; ldx #ROW ; 0-4
; ldy #COLUMN ; 0-4
; jsr BigPlot
; lda #"*"
; jsr $ffd2
; Or...
; jsr BigHome
; etc...
; Memory
SCR_PAGE = $0288 ; Holds screen page
CHAR_PAGE = $80 ; Character data page
LAST_CHAR = $d7 ; Character to print
CHAR = $d3 ; Address of character data (2 bytes)
SCR_PTR = $d1 ; Address of character draw (2 bytes)
BYTE1 = $c3 ; First bitmap byte in pair
BYTE2 = $c4 ; Second bitmap byte in pair
IX = $07 ; Index to bitmap character
COL_COUNT = $f9 ; Columns left before next row
ROW_COUNT = $fa ; Rows left before scroll
COL_PTR = $f3 ; Screen color pointer
CURR_COL = $0286 ; Current color code
SCROLL = $e975 ; Scroll routine
CLSR = $e55f ; Clear screen
SET_COL = $eab2 ; Calculate color pointer
* = $1800
; Initialize 5 Column Mode
Init5x5: jsr CLSR ; Clear screen
lda #<BigCharOut ; Set CHROUT vector
sta $0326 ; ,,
lda #>BigCharOut ; ,,
sta $0327 ; ,,
BigHome: ldx #0 ; Home character position
ldy #0 ; ,,
; Fall through to BigPlot
; Position Big Character
; Y is the COLUMN
; X is the ROW
; Backwards, like PLOT
BigPlot: sty COL_COUNT ; Set row and column counts to keep
stx ROW_COUNT ; track of scrolling and linefeeds
lda #0 ; Initialize screen pointer to top
sta SCR_PTR ; ,,
lda SCR_PAGE ; ,,
sta SCR_PTR+1 ; ,,
cpx #0 ; If plotting to first row, only do columns
beq just_col ; ,,
-loop: lda #88 ; Drop four lines down for each row
jsr ScreenAdd ; ,,
dex ; ,,
bne loop ; ,,
just_col: tya ; Add 4 for each column
asl
asl
; Fall through to ScreenAdd
; Add A to Screen Pointer
ScreenAdd: clc
adc SCR_PTR
sta SCR_PTR
bcc add_r
inc SCR_PTR+1
add_r: rts
; Write Big Char to Screen
; In A
BigCharOut: sta LAST_CHAR ; Store last character
pha ; Store registers, because that is
txa ; what's expected of a CHROUT
pha ; handler
tya ; ,,
pha ; ,,
lda LAST_CHAR ; Get character to print
cmp #$0d ; Handle linefeed character
bne non_lf ; ,,
ldy #0
ldx ROW_COUNT
inx
jsr BigPlot
jmp ch_row ; Advance to next row
non_lf: cmp #$20 ; Ignore everything else below space
bcs write ; ,,
jmp $e6dc ; Finish CHROUT
write: and #$bf ; Convert provided PETSCII value into a
bpl BigCode ; screen code, for character image lookup.
and #$7f ; ,,
ora #$40 ; ,,
BigCode: sta CHAR ; Set the character code in the screen
lda #$00 ; address
sta CHAR+1 ; ,,
ldy #3 ; Now multiply it by 8 (code x character size)
-loop: asl CHAR ; to get the character image offset address
rol CHAR+1 ; ,,
dey ; ,,
bne loop ; ,,
lda #CHAR_PAGE ; Then, get the full character image address
clc ; into CHAR by adding the character set
adc CHAR+1 ; page to the high byte
sta CHAR+1 ; ,,
ldx #3 ; Initialize X as row iterator
row_loop: ldy #0 ; BYTE 1 and BYTE2 are the next two bytes of
lda (CHAR),y ; character memory. We'll deal with all 8
sta BYTE1 ; rows of the character, two at a time
iny ; ,,
lda (CHAR),y ; ,,
sta BYTE2 ; ,,
txa ; (Store X, the iterator for rows, during
pha ; the column loop)
ldy #3 ; Likewise, we deal with 8 columns of each
-loop: lda BYTE2 ; pair of rows, two at a time.
and #%00000011 ; ,,
asl ; ,,
asl ; ,,
sta IX ; IX is the bitmap table index
lda BYTE1 ; The low two bits of the indexare in BYTE1
and #%00000011 ; ,,
ora IX ; Combine low and high two bits
tax ; Move the index to X
lda Bitmaps,x ; Get the proper chunky graphic character
sta (SCR_PTR),y ; Put it on the screen
jsr SET_COL ; Set the color pointer
lda CURR_COL ; Get the current color
sta (COL_PTR),y ; Set the color
lsr BYTE1 ; Shift bytes to get next pairs
lsr BYTE1 ; ,,
lsr BYTE2 ; ,,
lsr BYTE2 ; ,,
dey ; Iterator for columns
bpl loop ; ,,
lda #22 ; Drop pointer to next screen row for next
jsr ScreenAdd ; pair of rows
next_row: lda CHAR ; Advance character data pointer to the next
clc ; pair of rows
adc #2 ; ,,
sta CHAR ; ,,
bne dec_row ; ,,
inc CHAR+1 ; ,,
dec_row: pla ; Get the row iterator back and decrement
tax ; ,,
dex ; ,,
bpl row_loop ; ,,
lda SCR_PTR ; Advance the character pointer by subtracting
sec ; 88 characters (3 rows up = 88 - 5
sbc #84 ; characters to the right = 83)
sta SCR_PTR ; ,,
bcs in_col ; ,,
dec SCR_PTR+1 ; ,,
in_col: inc COL_COUNT ; Do we need linefeed?
ch_col: lda COL_COUNT ; ,,
cmp #5 ; ,,
bcc charout_r ; ,,
lda #0 ; If so, reset column count
sta COL_COUNT ; ,,
lda #68 ; Increment screen pointer by 68
jsr ScreenAdd ; (3 rows down = 66 + 2 to right = 68)
ch_row: inc ROW_COUNT ; Do we need to scroll?
lda ROW_COUNT ; ,,
cmp #5 ; ,,
bcc charout_r ; ,,
dec ROW_COUNT ; Set row count back to 4
jsr SCROLL ; Scroll 4 lines
jsr SCROLL ; ,,
jsr SCROLL ; ,,
jsr SCROLL ; ,,
lda SCR_PTR ; Back up 6 rows
sec ; ,,
sbc #132 ; ,,
sta SCR_PTR ; ,,
bcs charout_r ; ,,
dec SCR_PTR+1 ; ,,
charout_r: jmp $e6dc ; Finish CHROUT
; Character at Index N
; N bit 0 = Upper Right (y=even, x=odd)
; N bit 1 = Upper Left (y=even, x=even)
; N bit 2 = Lower Right (y=odd, x=odd)
; N bit 3 = Lower Left (y=odd, x=even)
Bitmaps: .byte 32,124,126,226,108,225,127,251
.byte 123,255,97,236,98,254,252,160
