More Sub-Routine Planning
Wrote Hardware VRAM Routines
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@ -1,6 +1,12 @@
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Kernel Routines Grouped by File
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Byte.S
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+- byte_flip
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+- byte_swap
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+- byte_drill
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Char.s
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+- char_to_lower
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5
main.s
5
main.s
@ -19,7 +19,7 @@ reset: sei
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lda #$E0
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sta vidm
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lda #$60
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sta cursor_delay
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lda #$06
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@ -44,6 +44,9 @@ reset: sei
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stz system_register
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stz soft_system_register
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jsr video_writeline_static
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.string "Hello World"
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jsr kernel_init
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54
src/kernel/byte.s
Normal file
54
src/kernel/byte.s
Normal file
@ -0,0 +1,54 @@
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byte_flip:
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; Byte Flip
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; Flips the Byte around
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; Position 0 gets swapped with 7
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; Position 1 gets swapped with 6 and so on...
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; Input:
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; A => Data
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; Output:
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; A <= Data
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rts
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byte_swap:
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; Byte Swap
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; Swaps the first 4 bits of the Byte
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; 0x0f (0b0000ffff) => 0xf0 (0bffff0000)
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; +----------+
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; | |
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; 0xcb | (0b1100 1011)
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; | |
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; | +----+
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; +----+ |
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; v v
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; 0xbc (0b1011 1100)
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; Input:
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; A => Data
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; Output:
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; A <= Data
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rts
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byte_drill:
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; Byte Drill
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; Converts two ASCII Characters, decoded in HEX to a byte
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; Not Case sensitive
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; Input:
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; A => First ASCII
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; X => Last ASCII
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; Output:
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; A <= Converted Byte
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; First Char => "FF" <= Last Char
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rts
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@ -10,6 +10,15 @@ vram_write:
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; Output: (none)
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; Load Data into Registers
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stx vidx ; Sets Read Mode, load X Coord
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sty vidy ; load Y Coord
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sta vidd ; Set Write Mode, load Data
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nop ; Wait a bit...
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nop
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nop
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nop
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stx vidx ; Sets Read Mode
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rts
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@ -25,6 +34,23 @@ vram_write_color:
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; Output: (none)
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; I'm deliberately NOT using Kernel Stack here,
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; for more speed and efficiency and because It's just one Byte
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pha ; Push A to Stack
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txa ; Transfer X to A for Math
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adc #$40 ; Add #$40 (Color Range)
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plx ; Pop Stack to X
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; Load Data into Registers
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sta vidx ; Sets Read Mode, load X Coord
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sty vidy ; load Y Coord
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stx vidd ; Set Write Mode, load Data
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nop ; Wait a bit...
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nop
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nop
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nop
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sta vidx ; Sets Read Mode
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rts
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@ -39,6 +65,14 @@ vram_read:
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; Output:
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; A <= Data
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; Load Data into Registers
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stx vidx ; Set to Read Mode, load X Coord
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sty vidy ; load Y Coords
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nop ; Wait a bit...
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nop
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nop
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nop
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lda vidd ; Load Data
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rts
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@ -1,5 +1,45 @@
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irq_init:
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; IRQ Init
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; Initialises the VIA to be resetted into a normal state and
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; to generate a constand IRQ Tick (Timer 1)
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; Input:
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; A => Timer 1 Tick Rate (MSB)
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; Output: (none)
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sta t1ch
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lda #$40
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sta acr
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stz t1cl
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lda #$00
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sta ier
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cli
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rts
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irq:
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; IRQ
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; This is the Standart IRQ Routine
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; It scans the Keyboard, invokes the Tick Event Handler
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; and does some other, housekeeping stuff
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; Input: (none)
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; Output: (none)
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php ; Save Processor Status, A, X and Y
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sta irq_a
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stx irq_x
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sty irq_y
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bit t1cl ; "Ping" VIA Timer, to trigger Restart
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lda irq_a ; Restore A, X, Y and Processor Status
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ldx irq_x
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ldy irq_y
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plp
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rti
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@ -21,7 +21,7 @@ k7 = $20c ; 8 bit
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keyboard_current = $20d ; 8 bit Held Keyboard Key, without Formatting (shift, etc.) "Scan Key"
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keyboard_previous = $20e ; 8 bit Previous held "Scan Key"
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keyboard_format = $20f ; 8 bit Formatted Char, from keyboard_current
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keyboard_ascii = $20f ; 8 bit Formatted Char, from keyboard_current as ASCII
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keyboard_arrow = $210 ; 8 bit Held Arrow Keys
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keyboard_modifier = $211 ; 8 bit Held Modifier Keys, such as "shift, alt, control"
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@ -41,11 +41,11 @@ soft_system_register = $21d ; 8 bit (internal)
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color = $21e ; 8 bit Fore & Background Color
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typelength = $21f ; 8 bit Length of typebuffer
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kernel_stack = $280 ; 256 bytes 256 byte, Kernel Stack, used for offloading Registers
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kernel_stack = $300 ; 256 bytes 256 byte, Kernel Stack, used for offloading Registers
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typebuffer = $380 ; 256 bytes 256 byte, All Purpose Char Buffer
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typebuffer = $400 ; 256 bytes 256 byte, All Purpose Char Buffer
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; END => $480
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; END => $500
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; Hardware Registers
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@ -82,9 +82,9 @@ system_register = $bc00 ; 8 bit System Register
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;-----------------------------------------------------------------------------------------------
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; $200-$27f: Kernel Variables
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;-----------------------------------------------------------------------------------------------
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; $280-$37f: Kernel Stack
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; $300-$3ff: Kernel Stack
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;-----------------------------------------------------------------------------------------------
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; $380-$47f: Typebuffer
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; $400-$4ff: Typebuffer
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;-----------------------------------------------------------------------------------------------
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;
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;-----------------------------------------------------------------------------------------------
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