MotorDecoderInterface/Lab8Reference.asm at main · izou3/MotorDecoderInterface · GitHub

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; Starting code with basic constants and simple subroutine

ORG 0
Start:
	IN    Quad
	CALL  Mod6
	CALL  DisplayWithNeg
	JUMP  Start

;******************************************************************************
; Abs: 2's complement absolute value
; Returns abs(AC) in AC
; Negate: 2's complement negation
; Returns -AC in AC
;******************************************************************************
Abs:
	JPOS   Abs_r        ; If already positive, return
Negate:
	XOR    NegOne       ; Flip all bits
	ADDI   1            ; Add one
Abs_r:
	RETURN

DisplayWithNeg:
	CALL   Abs
	OUT    Hex1
	CALL   Negate
	OUT    Hex0
	RETURN

Mod6:
	JZERO  End
	JNEG   Mod6Neg
L:	ADDI   -6
	JPOS   L ; loops until number is negative / zero
	JZERO  End
EndPos:
	ADDI   6
	JUMP   End
Mod6Neg:
	ADDI   6
	JNEG   Mod6Neg ; loops until number is positive / zero
End:
	RETURN


; Useful values
Zero:      DW 0
NegOne:    DW -1
One:
Bit0:      DW &B0000000001
Bit1:      DW &B0000000010
Bit2:      DW &B0000000100
Bit3:      DW &B0000001000
Bit4:      DW &B0000010000
Bit5:      DW &B0000100000
Bit6:      DW &B0001000000
Bit7:      DW &B0010000000
Bit8:      DW &B0100000000
Bit9:      DW &B1000000000
LoByte:    DW &H00FF
HiByte:    DW &HFF00


; IO address constants
Switches:  EQU &H000
LEDs:      EQU &H001
Timer:     EQU &H002
Hex0:      EQU &H004
Hex1:      EQU &H005
Incr:      EQU &H0F0
Quad:      EQU &H0F1