More Sub-Routine Planning

Wrote Hardware VRAM Routines

KernelRoutineList.txt

@@ -1,6 +1,12 @@
 Kernel Routines Grouped by File
 
 
+Byte.S
+  |
+  +- byte_flip
+  +- byte_swap
+  +- byte_drill
+
 Char.s
   |
   +- char_to_lower

main.s

@@ -44,6 +44,9 @@ reset:      sei
             stz system_register
             stz soft_system_register
 
+            jsr video_writeline_static
+            .string "Hello World"
+
 
             jsr kernel_init
 

src/kernel/byte.s

@@ -0,0 +1,54 @@
+byte_flip:
+            ; Byte Flip
+            ; Flips the Byte around
+            ; Position 0 gets swapped with 7
+            ; Position 1 gets swapped with 6 and so on...
+
+            ; Input:
+            ; A => Data
+            
+            ; Output:
+            ; A <= Data
+
+
+            rts
+
+byte_swap:
+            ; Byte Swap
+            ; Swaps the first 4 bits of the Byte
+            ; 0x0f (0b0000ffff) => 0xf0 (0bffff0000)
+
+            ;         +----------+
+            ;         |          |
+            ; 0xcb    | (0b1100 1011)
+            ;         |     |
+            ;         |     +----+
+            ;         +----+     |
+            ;              v     v
+            ; 0xbc      (0b1011 1100)
+
+            ; Input:
+            ; A => Data
+            
+            ; Output:
+            ; A <= Data
+
+
+            rts
+
+byte_drill:
+            ; Byte Drill
+            ; Converts two ASCII Characters, decoded in HEX to a byte
+            ; Not Case sensitive
+
+            ; Input:
+            ; A => First ASCII 
+            ; X => Last ASCII
+            
+            ; Output:
+            ; A <= Converted Byte
+            
+            ; First Char => "FF" <= Last Char
+
+
+            rts

src/kernel/hardware.s

@@ -10,6 +10,15 @@ vram_write:
 
             ; Output:  (none)
 
+                        ; Load Data into Registers
+            stx vidx    ; Sets Read Mode, load X Coord
+            sty vidy    ; load Y Coord
+            sta vidd    ; Set Write Mode, load Data
+            nop         ; Wait a bit...
+            nop
+            nop
+            nop
+            stx vidx    ; Sets Read Mode
 
             rts
             
@@ -25,6 +34,23 @@ vram_write_color:
             
             ; Output:  (none)
 
+            ; I'm deliberately NOT using Kernel Stack here,
+            ; for more speed and efficiency and because It's just one Byte
+
+            pha         ; Push A to Stack
+            txa         ; Transfer X to A for Math
+            adc #$40    ; Add #$40 (Color Range)
+            plx         ; Pop Stack to X
+
+                        ; Load Data into Registers
+            sta vidx    ; Sets Read Mode, load X Coord
+            sty vidy    ; load Y Coord
+            stx vidd    ; Set Write Mode, load Data
+            nop         ; Wait a bit...
+            nop
+            nop
+            nop
+            sta vidx    ; Sets Read Mode
 
             rts
 
@@ -39,6 +65,14 @@ vram_read:
             ; Output:
             ; A <= Data
 
+                        ; Load Data into Registers
+            stx vidx    ; Set to Read Mode, load X Coord
+            sty vidy    ; load Y Coords
+            nop         ; Wait a bit...
+            nop
+            nop
+            nop
+            lda vidd    ; Load Data
 
             rts
 

src/kernel/irq.s

@@ -1,5 +1,45 @@
 irq_init:
+            ; IRQ Init
+            ; Initialises the VIA to be resetted into a normal state and
+            ; to generate a constand IRQ Tick (Timer 1)
+
+            ; Input:
+            ; A => Timer 1 Tick Rate (MSB)
+
+            ; Output: (none)
+
+            sta t1ch
+            
+            lda #$40
+            sta acr
+            stz t1cl
+            lda #$00
+            sta ier
+            cli
+
             rts
 
 irq:
+            ; IRQ
+            ; This is the Standart IRQ Routine
+            ; It scans the Keyboard, invokes the Tick Event Handler
+            ; and does some other, housekeeping stuff
+
+            ; Input:  (none)
+            ; Output: (none)
+
+
+            php         ; Save Processor Status, A, X and Y
+            sta irq_a
+            stx irq_x
+            sty irq_y
+
+
+
+            bit t1cl    ; "Ping" VIA Timer, to trigger Restart
+            lda irq_a   ; Restore A, X, Y and Processor Status
+            ldx irq_x
+            ldy irq_y
+            plp
+
             rti

src/variables.s

@@ -21,7 +21,7 @@ k7                      = $20c      ; 8 bit
 
 keyboard_current        = $20d      ; 8 bit                 Held Keyboard Key, without Formatting (shift, etc.) "Scan Key"
 keyboard_previous       = $20e      ; 8 bit                 Previous held "Scan Key"
-keyboard_format         = $20f      ; 8 bit                 Formatted Char, from keyboard_current
+keyboard_ascii          = $20f      ; 8 bit                 Formatted Char, from keyboard_current as ASCII
 keyboard_arrow          = $210      ; 8 bit                 Held Arrow Keys
 keyboard_modifier       = $211      ; 8 bit                 Held Modifier Keys, such as "shift, alt, control"
 
@@ -41,11 +41,11 @@ soft_system_register    = $21d      ; 8 bit     (internal)
 color                   = $21e      ; 8 bit                 Fore & Background Color
 typelength              = $21f      ; 8 bit                 Length of typebuffer
 
-kernel_stack            = $280      ; 256 bytes             256 byte, Kernel Stack, used for offloading Registers
+kernel_stack            = $300      ; 256 bytes             256 byte, Kernel Stack, used for offloading Registers
 
-typebuffer              = $380      ; 256 bytes             256 byte, All Purpose Char Buffer
+typebuffer              = $400      ; 256 bytes             256 byte, All Purpose Char Buffer
 
-; END => $480
+; END => $500
 
 
 ; Hardware Registers
@@ -82,9 +82,9 @@ system_register         = $bc00     ; 8 bit                 System Register
 ;-----------------------------------------------------------------------------------------------
 ; $200-$27f:            Kernel Variables
 ;-----------------------------------------------------------------------------------------------
-; $280-$37f:            Kernel Stack
+; $300-$3ff:            Kernel Stack
 ;-----------------------------------------------------------------------------------------------
-; $380-$47f:            Typebuffer
+; $400-$4ff:            Typebuffer
 ;-----------------------------------------------------------------------------------------------
 ;
 ;-----------------------------------------------------------------------------------------------