****************************************************************************
* EE113L - Fall 2000 Final Project
* 
* Reed Solomon Encoder - Main Program
* 
* Created by Kenny Kwan and David Lee
* December 4, 2000
*****************************************************************************

	.setsect ".data",   0x5000,1
	.setsect ".text",   0x500,0

;=========================data for encoding====================
.data

pb		.word	0,0,0,0,0,0				; Parity Bits aka bb
indata		.word	5,5,5,5,5,5,5,5,5       		; In Data
alpha		.word   1,2,4,8,3,6,12,11,5,10,7,14,15,13,9,0   ; Galois Field Coeff
index		.word   -1,0,1,4,2,8,5,10,3,14,9,7,6,13,11,12   ; Index Field
gg		.word   6,9,6,4,14,10,0,0,0,0,0,0,0,0,0,0       ; Generator Polymonial Coeff
feedback 	.word 	0
counti		.word	8					; i counter
countj		.word	5					; j counter

;==============================================================
	.text
;============ Main Code ===========

		AR0 = #540h		; Memory address of counti

mainloop	nop
		A = *AR0
		if(ALT) goto done

		AR7 = #505h		; AR7 points to mem location 1005, pb[5]
		A = *AR7		; Store value of pb[5] in Acc. A
		nop
		nop
		AR7 = #indata
		B = AR7		; Mem address of first data point
		nop
		nop
		B = B + *AR0
		AR7 = B
		nop
		nop
		B = *AR7		; Store value of data[counti] in Acc B
		nop
		nop
		A = A ^ B		; Acc A = data[counti] XOR pb[5]

		AR7 = A
		nop
		nop
		AR6 = #index
		A = AR6
		nop
		nop
		B = AR7
		nop
		nop
		A = A + B		; Points to Index[ data[counti] XOR pb[5] ]

		AR6 = #feedback
		AR7 = A
		nop
		nop
		A = *AR7
		*AR6 = A		; Store the value in Index[ data[counti] XOR pb[5] ] into feedback memory location
		nop
		nop

		A = *AR6		; Store value of feedback into Acc A
		nop
		nop
		if (ALT) goto else1	; If Acc A < 0 goto else1

		AR1 = #countj		; Store location of countj into AR1
		*AR1 = #5

innerloop	AR1 = #countj		; Store location of countj into AR1
		A = *AR1
		nop
		nop
		if(AEQ)	goto finishinner

		AR7 = #gg
		A = AR7
		nop
		nop
		B = *AR1
		nop
		nop
		A = A + B
		AR7 = A			; Mem location of gg[countj] stored in AR7
		nop
		nop
		A = *AR7		; Store value of gg[countj] into Acc A
		nop
		nop
		
		if (ALT) goto else2	; If gg[countj] < 0 then goto else2

		AR6 = #feedback
		B = *AR6
		nop
		nop
		A = A + B		; Acc A = value of gg[countj] + feedback
		
		;============ Calculate (gg[countj] + feedback) MOD 15 ===================

		B = A
		A = A - #15
		if (AEQ) goto equal30	; If less than or equal to 15 goto less15
		if (ALT) goto less15
		goto less30


less15	A = B			; Store MOD value in Acc A
		goto continue

less30	B = A
		A = A - #15
		if (AEQ) goto equal30	; If the sum = 30 then MOD result should equal 0, therefore goto equal30
		A = B			; Store MOD value in Acc A

		goto continue
equal30		A = #0		

		;=========================================================================

continue	AR7 = #alpha		; Store first alpha memory location into AR7
		B = AR7
		nop
		nop
		A = A + B		; Mem location of alpha[junk MOD 15]
		AR7 = A			; Store correct alpha memory location index into AR7
		nop
		nop

		AR6 = #pb
		A = *AR1
		nop
		nop
		A = A - #1
		B = AR6
		nop
		nop
		A = A + B		; Memory location of pb[countj-1]
		AR6 = A
		nop
		nop
		B = *AR7		; Store value of alpha[junk MOD 15] into B
		nop
		nop
		A = *AR6		; Store value of pb[countj - 1] into A
		nop
		nop
		A = A ^ B		; Acc A = pb[countj - 1] XOR alpha[junk MOD 15]
		AR7 = #pb
		B = *AR1
		nop
		nop
		B = B + #500h		; Mem location of pb[countj]
		AR7 = B
		nop
		nop
		*AR7 = A		; Stuff Acc A into pb[countj]
		nop
		nop
		goto jcount
		

else2		AR7 = #pb
		A = #AR7
		nop
		nop
		A = A + *AR1		; Mem location of pb[countj]
		AR7 = A
		nop
		nop
		A = A - #1		; Mem location of pb[countj - 1]
		AR6 = A
		nop
		nop
		A = *AR6
		*AR7 = A		; Set pb[countj] = pb[countj - 1]
		nop
		nop
		goto jcount



finishinner	AR7 = #pb
		AR6 = #feedback
		AR5 = #gg
		A = *AR6
		nop
		nop
		A = A + *AR5		; Value of gg[0] + feedback

		;============ Calculate (gg[0] + feedback) MOD 15 ===================

		B = A
		A = A - #15
		if (AEQ) goto equal30b	; If less than or equal to 15 goto less15
		if (ALT) goto less15b
		goto less30b

less15b	A = B			; Store MOD value in Acc A
		goto continue2

less30b	B = A
		A = A - #15
		if (AEQ) goto equal30b	; If the sum = 30 then MOD result should equal 0, therefore goto equal30
		A = B			; Store MOD value in Acc A
		goto continue2
equal30b	A = #0		
		
		;=========================================================================

continue2	AR7 = #alpha
		B = AR7
		nop
		nop
		A = A + B		; Memory location of alpha[junk MOD 15]
		AR6 = A
		nop
		nop
		A = *AR6		; Put value of alpha[junk MOD 15] into Acc A
		nop
		nop
		AR7 = #pb
		*AR7 = A		; pb[0] = alpha[junk MOD 15]
		nop
		nop
		goto icounter
		
jcount		AR1 = #countj	
		A = *AR1
		nop
		nop
		A = A - #1
		*AR1 = A
		nop
		nop
		goto innerloop
	;======= if block 1 end ================

else1		AR7 = #505h
		AR6 = #504h
		A = *AR6-
		nop
		nop
		*AR7- = A		; pb[5] = pb[4]
		nop
		nop
		A = *AR6-
		nop
		nop
		*AR7- = A		; pb[4] = pb[3]
		nop
		nop
		A = *AR6-
		nop
		nop
		*AR7- = A		; pb[3] = pb[2]
		nop
		nop
		A = *AR6-
		nop
		nop
		*AR7- = A		; pb[2] = pb[1]
		nop
		nop
		A = *AR6-
		nop
		nop
		*AR7- = A		; pb[1] = pb[0]
		nop
		nop

		*AR7 = #0		; pb[0] = #0

icounter	AR0 = #counti
		A = *AR0
		nop
		nop
		A = A - #1
		*AR0 = A
		nop
		nop
		goto mainloop

;============ End Program =========		
done	nop
	goto   done

	.end