In a serial input-output circuit comprising a memory device (15) for memorizing an input serial bit sequence as memorized bit groups, each consisting of a predetermined number of parallel bits, first and second bidirectional shift registers (21, 22) are serially connected through a ring connection (24,...http://www.google.com/patents/US4959813?utm_source=gb-gplus-sharePatent US4959813 - Serial input-output circuit for forward and backward producing bits from bidirectional shift registers
