A traditional principle has been that with a mortgage you can only guarantee an obligation. This must be understood in its correct sense: thus, in the frequent case of a mortgage loan, what was meant is that a mortgage could only guarantee a specific loan; and, in general to an obligation would correspond, in his case, a mortgage.

But, even in the case of a mortgage-a loan, the mortgage guarantees the various benefits of the debtor that derive from its obligation; thus, in the case of a loan, having to be well determined, the return of the capital, ordinary interest, late interest, costs and expenses, etc. is covered.

However, this principle is under review, and it can be affirmed that a mortgage can, in certain cases, guarantee several obligations.

 Different can receive a single mortgage coverage when they have causal connection with each other or dependence on one another
And adds:

On a purely literalist interpretation of Articles 1876 of the Civil Code (CC) and 104 of the Mortgage Law (LH) must prevail that with logical, systematic and finalist results from other legal provisions, such as Article 1861 of the Code itself or 154 and 155 of the LH, and attending to the needs of the legal traffic.
In effect, the DGRN continues:

Undoubtedly, different obligations can receive a single mortgage coverage when they have causal connection with each other or dependence on one another. It is not prevented by the application of the specialty principle or the accessory of the mortgage, insofar as the different obligations are determined in their defining aspects (or at least these are determinable, as -with notable flexibility, in order to facilitate credit -It is allowed in some cases, provided that certain minimum requirements are met) and the mortgage constituted is linked to these different obligations so that it is duly subject to them at birth, validity and enforceability.
And concludes the DGRN:

When these various obligations guaranteed by a unitary mortgage relationship are not subject to the same legal regime and have different title to achieve their mortgage effectiveness, it will be necessary, in principle and for requirements of determination of the real right constituted - Articles 9 and 12 LH -, establish separately the amount that respect of each obligation will cover the guarantee.