London — The divided communities of Northern Ireland are getting a fresh chance to sink their differences and give the violence and religious animosity a chance to heal.
Their opportunity comes in the shape of a program of ''rolling devolution'' unveiled by Secretary for Northern Ireland James Prior. The plan is on its way through the British Parliament.
Under Mr. Prior's plan, which has been months in the making, Britain will establish a provincial 78-member assembly in Northern Ireland. The new body would be elected in the autumn, and its members would be invited to expand their influence by designing a framework to return power to local authorities.
The program stipulates that the assembly's proposals must be acceptable to both Roman Catholics and Protestants. By requiring 70 percent majority before portfolios can be created, Britain knows that there must be cooperation between the two communities.
If there is cooperation, the assembly will begin to take the form of a full-scale parliament through mutual agreement. But if there is not, Ulster will continue to be ruled directly from London. Thus the responsibility rests with the Ulstermen.
It is also hoped that the new assembly will help to siphon away support from Protestant and Catholic men of violence, whose popularity has been waning anyway.
It will also provide a forum in which Ulster's economic plight may be discussed by elected representatives.
Said one British official, ''The people of Ulster know their economy is in a mess. The assembly will enable them to consider the economic options, including self-help. If enough Protestants and Catholics can find common ground, the assembly will begin flowering, with executive ministers who can start to take charge of events.''
The Thatcher Cabinet is solidly behind the setting up of the assembly and the government has an assured majority for passage of the law required to establish it.
Mr. Prior is aware that strong resistance to his plan already exists. The prominent Ulster Unionist, Enoch Powell, has condemned it as a constitutional monstrosity, but the British government is determined to create the new structure.
It belives the will of Ulsters' rank-and-file citizens is behind the rolling devolution program.
Contributor Alf McCreary reports from Belfast:
The British government's latest proposals for limited self-government in Northern Ireland have been greeted by the predictable hostility of the main parties in the province.
But fears are growing that hard-line Ulster Unionists (British loyalists) could mold a new assembly for their own purposes to set up their own government, if the British continue to oppose majority Protestant rule.
Mr. William Craig, an official Unionist who was a former Cabinet minister in the previous Northern Ireland parliament (suspended in 1972 by the British after widespread community violence), has described the new proposals as a recipe for conflict on a scale ''not yet seen.''
The proposals, Mr. Craig said, were incapable of producing political stability. The task now was to ''bury the initiative'' announced by the British, he said.
However, he said that the proposed elections should take place and the Unionists should band together to establish a ''de facto'' government that would have a mandate and in that sense would have power.
Mr. Craig was voicing fears expressed privately by other politicians that an assembly would be a ready-made vehicle that could be politically hijacked by a majority group on a collision course with Britain.
The British have stated repeatedly that Roman Catholics should be allowed to share power with the Protestants who outnumber Catholics by 2 to 1.
Prior's proposals can hardly be faulted on analysis of Ulster's divisions, but their success depends on the one thing that no British politician can deliver, namely the political will of Ulster politicians to find a solution.