An equally divided Supreme Court yesterday affirmed a Massachusetts ruling that the constitutional protection against self-incrimination hadn't been waived "knowingly and intelligently" by a motorist found by a state trooper to be so drunk that "he didn't know what he was doing."

Because the court split 4 to 4, the affirmance will control in any similar cases in Massachusetts -- but nowhere else.

The court acted with an unsigned, one-sentence opinion. Justice Lewis F. Powell Jr., who could have provided a decisive vote, took no part in considering or deciding the case. He gave no reason.

The requirement for a knowing and intelligent waiver of rights by suspects without counsel was laid down by the court in 1966 in the so-called Miranda case. Evidence obtained in violation of Miranda rights must be wuppressed.

Acting yesterday in crminal, Miranda and cases of other types, the court also:

Granted a Justice Department petition to review a ruling, in a case involving former Rep. Henry Helstoski (D-N.J.), that the government says would make bribery prosecutions of present or former members of Congress "virtually impossible in a large number of cases."

Agreed to decide, in a case involving a former congressman and mayor, Hugh J. Addonizio (D) of Newark, N.J., whether a U.S. district judge may revise a lawful sentence because the federal Parole Commission has "'frustrated his sentencing intent."

Rescinded as "improvidently granted," but without explanation, its agreement to review a Georgia state judge's ruling under which an indigent convicted burglar, put on probation on condition that she pay a $165 fine, was imprisoned after her plans to raise the money fell through.

Upheld, 6 to 3, a New Jersey disparate sentencing structure under which life imprisonment is mandatory for a defendant convicted by a jury of first-degree murder, while either a 30-year sentence or life can be imposed if the defendant pleads no contest.

Agreed to review a 4-to-o ruling by a New York State court validating warrantles arrests of suspects in their homes even though police officers had had plenty of time to get warrants.

Agreed, in a North Carolina Miranda case, to review a ruling that an incriminating statement obtained from a defendant had to be suppressed because he hadn't waived his right to counsel in writing and hadn't been shown to have made a specific oral waiver "knowingly."

Declined, in a Louisiana Miranda case, to review a state court decision that a 13-year-old boy hadn't acted voluntarily when he confessed to the killing of a 9-year-old neighbor girl, and that neither he nor his parents had knowingly waived his right to counsel and his privilege against self-incrimination.

Upheld -- in the first unanimous decision of the current term -- the Department of Health, Education, and Welfare's rule that the "right to travel" doesn't prevail over an HEW rule for Supplemental Security Income benefits for the needy aged, blind and disabled: a recipient who spends an entire month outside the United States loses benefits for that month.

Agreed, in a Massachusetts case. to rule on whether HEW infringes on the constitutional guarantee of equal protection of the laws by paying benefits intended to aid needy "dependent" children when the father is out of work, but denying them when the mother becomes unemployed.

The Helstoski case arose from an indictment a week before the 1976 Democratic primary, in which he lost a bid for renomination to a seventh House term. He has yet to be tried on the indictment, in which he is accused of conspiring to accept, and of accepting, bribes in connection with the introduction of bills to let specified individuals immigrate into the United States.

Last April, the 3rd U. S. Circuit Court of Appeals ruled that the Constitution's "speech or debate clause," which makes a representative or a senato accountable only to the House or Senate for his legislative acts, prevents the government from introducing at trial any reference to past legislative acts. The court also ruled that Helstoski, in voluntarily cooperating with the prosecution before be was indicted, hadn't waived his immunity.

The Supreme Court granted the government's petition for review of these phases of the 3rd Circuit ruling.

At the same time, however, the High Court granted Helstoski's petition for review of other phases of the ruling, in which the appeals court held that the speech-or-debate clause did not bar the grand jury from hearing evidence about the bills he introduced and also did not bar the indictment.

Helstoski, who says he's innocent, charged that the 3rd Circuit ruling would let the executive branc "use the grand jury unconstitutionally to obtain an unconstitutional indictment" and to "intrude upon legislative immunity."

Former Newark mayor Addonizio, convicted of 63 counts of extortion in connection with city procurement of supplies, began in March 1972 to serve a 10-year sentence imposed by U.S. District Court Judge George H. Barlow.

He became eligible for parole July 3, 1975, but the Parole Commission decided he couldn't be released until January 1977. At that time it insisted that he serve the full 10 years, despite his good behavior in prison, because of the enormity of his breach of public trust.

But Barlow, affirmed last February by the 3rd Circuit, ordered Addonizio released, and he has been free since May 12, 1977. The judge said that the gravity of the offense had been considered by him, that he hadn't expected the commission to take it into account, and that he had expected Addonizio to serve 3 1/2 to 4 years.