S.D. Codified Laws § 23-24A-3
Whenever a person has entered upon a term of imprisonment in a penal or correctional institution of a party state, and whenever during the continuance of the term of imprisonment there is pending in any other party state any untried indictment, information, or complaint on the basis of which a detainer has been lodged against the prisoner, he shall be brought to trial within one hundred eighty days after he shall have caused to be delivered to the prosecuting officer and the appropriate court of the prosecuting officer's jurisdiction written notice of the place of his imprisonment and his request for a final disposition to be made of the indictment, information, or complaint: provided that for good cause shown in open court, the prisoner or his counsel being present, the court having jurisdiction of the matter may grant any necessary or reasonable continuance.
SDCL 23-24A-3