Tennessee Code Title 47. Commercial Instruments and Transactions § 47-50-112

(a) All contracts, including, but not limited to, notes, security agreements, deeds of trust, and installment sales contracts, in writing and signed by the party to be bound, including endorsements thereon, shall be prima facie evidence that the contract contains the true intention of the parties, and shall be enforced as written; provided, that nothing herein shall limit the right of any party to contest the agreement on the basis it was procured by fraud or limit the right of any party to assert any other rights or defense provided by common law or statutory law in regard to contracts.

(b) Any contract, security agreement, note, deed of trust, or other security instrument, in writing and signed or endorsed by the party to be bound, that provides that the security interest granted therein also secures other provisions or future indebtedness, regardless of the class of other indebtedness, be it unsecured, commercial, credit card, or consumer indebtedness, shall be deemed to evidence the true intentions of the parties, and shall be enforced as written; provided, that nothing herein shall limit the right of any party to contest the agreement on the basis that it was procured by fraud or limit the right of any party to assert any other rights or defense provided by common law or statutory law in regard to contracts.

(c) If any such security agreement, note, deed of trust, or other contract contains a provision to the effect that no waiver of any terms or provisions thereof shall be valid unless such waiver is in writing, no court shall give effect to any such waiver unless it is in writing.