; https://sites.google.com/site/6502asembly/code-examples/arithmetic/crc32_add
;---------------------------------------------
;CRC32_add
; Purposes:
;	1. Add the CRC32 Checksum
; Input: 
; Output:
; Required Variables:
; Required Functions:
; Required Table:
; Labels used:
;	1. CRC32_add:
;	2. LOOP2:
;	3. COMPL2:
; Variables used:
;	1. CRC...CRC+3
;	2. tmp3:tmp2
; Constant used:
; Function used:
; Used by:
; Version: 1.0
; Revision Date: 28/8/2006
;---------------------------------------------
CRC32_add:
	LDY #$FF  ; A0 FF
	STY  CRC  ; 
	STY CRC+1
	STY CRC+2
	STY CRC+3
	INY
LOOP2   LDA  (tmp2)
	INC tmp2
	EOR CRC	 ; Quick CRC computation with lookup tables
	TAX
	LDA  CRC+1
	EOR CRCT0,X
	STA CRC
	LDA  CRC+2
	EOR CRCT1,X
	STA  CRC+1
	LDA  CRC+3
	EOR CRCT2,X
	STA CRC+2
	LDA  CRCT3,X
	STA  CRC+3
	INY
	CPY crc_len
	BNE LOOP2
	LDY #3
COMPL2  LDA  CRC,Y
	EOR #$FF
	STA  CRC,Y
	DEY
	BPL  COMPL2
	;add CRC registers to the end
	LDA  CRC+3
	STA  (tmp2)
	INC tmp2
	LDA  CRC+2
	STA  (tmp2)
	INC tmp2
	LDA CRC+1
	STA  (tmp2)
	INC tmp2
	LDA  CRC

	STA (tmp2)
	RTS
;End of CRC32_add
;---------------------------------------------

;---------------------------------------------
;Memory_Copy:
; Purposes:
;	1. Copy a predined block of memory to specific address.
; Input: 
;	1. Source: tmp3:tmp2
;	2. Destination: tmp5:tmp4
;	3. Length: X
; Output:
; Required Variables:
; Required Functions:
; Required Table:
; Labels used:
; Variables used:
; Constant used:
; Function used:
; Used by:
; Version: 1.0
; Revision Date: 28/8/2006
;---------------------------------------------
Memory_Copy:
	LDA (tmp2)
	STA (tmp4)
	INC tmp2
	BNE Memory_Copy_01
	INC tmp3
Memory_Copy_01:
	INC tmp4
	BNE Memory_Copy_02
	INC tmp5
Memory_Copy_02:
	DEX
	BNE Memory_Copy 
Memory_Copy_Exit:
	RTS
;End of Memory_Copy
;---------------------------------------------