I never worked with a PDPS, but only with the other P types. If it is the same, the subroutine will start at COM 2102D.
Just recognized your previous post. "R" stands for relative memory adress. The memory adress of an xxR command is command value + adress register. The adress register is manipulated with xAx commands like LAW = load constant value, LAA = load memory value, AAW = add constant value.