BGScroll.cs

    public float scrollSpeed = 0;
    public Vector3 direction;

    private Vector3 startPos;

	// Use this for initialization
	void Start () {
        startPos = transform.position;
	}
	
	// Update is called once per frame
	void Update () {
        float newPos = Mathf.Repeat(Time.time * scrollSpeed, GetComponent<SpriteRenderer>().bounds.size.y);
        transform.position = startPos + direction * newPos;
	}