initial import from 8bitworkshop.com

8bitunity.asm

@@ -0,0 +1,92 @@
+
+	processor 6502
+	seg.u ZEROPAGE	; uninitialized zero-page variables
+	org $0
+
+_hiresLinesHI = $00
+_hiresLinesLO = $01
+
+
+hiresXZP = $ec
+hiresYZP = $ed
+hiresAddrZP = $fc
+inputAddrZP = $fa
+outputAddrZP = $ee
+scr2outRowsZP = $ce
+inp2scrRowsZP = $eb
+bytesPerRowZP = $e3
+toggleMainAuxZP = $42
+
+	seg CODE
+	org $803	; starting address
+
+Start
+	jmp Start	; endless loop
+        
+        
+        
+        ldx #0
+loopRow:
+	; Copy Screen Address from Hires Tables (using Line Offset Y and Byte Offset X)
+	ldy hiresYZP			; Y-Offset to Hires Line
+	lda _hiresLinesHI,y
+	sta loopCopy1+2			; LDA $HIlo,Y  -- SMC -- +2 cycle
+        sta loopCopy2+5			; STA $HIlo,Y  -- SMC -- +5 cycles
+	lda _hiresLinesLO,y
+	adc hiresXZP			; X-Offset to Hires Byte
+	sta loopCopy1+1			; LDA $hiLO,Y  -- SMC -- +2 cycle
+        sta loopCopy2+8			; STA $hiLO,Y  -- SMC -- +5 cycles
+	
+	; Copy bytes from SHR buffer to ouput	
+screen2output:
+	lda outputAddrZP+1
+	beq input2screen  ; If high-byte is zero, then skip
+	ldy #0				; Y loop: Copy xxx bytes per row
+loopCopy1:				; Copy 1 byte
+	lda $2000,y			; SMC: -1 cycle /byteperrow / line 
+	sta (outputAddrZP),y
+	iny					
+	cpy bytesPerRowZP
+	bne loopCopy1			; Iterate Y loop
+	
+	; Copy bytes from input to SHR buffer
+	cpx inp2scrRowsZP		; Check number of input rows (for cropped sprites)
+	bcs incAddress1
+input2screen:	
+	clc
+	lda inputAddrZP+1
+	beq incAddress1   ; If high-byte is zero, then skip	
+	ldy #0				; Y loop: Copy xxx bytes per row
+loopCopy2:
+	lda (inputAddrZP),y		; Copy 1 byte
+	sta $2000,y			; SMC: -1 cycle / byteperrow / line
+	iny					
+	cpy bytesPerRowZP		; Iterate Y loop
+	bne loopCopy2
+		
+incAddress1:
+	clc				; Increment address of output block
+	lda outputAddrZP			
+	adc bytesPerRowZP	; Move by xxx bytes
+	sta outputAddrZP	
+	bcc nocarry1		; Check if carry to high-byte
+	inc outputAddrZP+1
+nocarry1:
+	
+incAddress2:
+	clc				; Increment address of input block
+	lda inputAddrZP			
+	adc bytesPerRowZP	; Move by xxx bytes
+	sta inputAddrZP	
+	bcc nocarry2		; Check if carry to high byte
+	inc inputAddrZP+1
+nocarry2:
+
+nextRow:
+	; Move to next row
+	inc hiresYZP		; Increment Hires Line offset
+	inx				
+	cpx scr2outRowsZP
+	bcc loopRow		; Iterate X loop (rows)
+	
+	rts