The 71V3559 3.3V CMOS Synchronous SRAM is organized as 256K x 18. It is designed to eliminate dead bus cycles when turning the bus around between reads and writes, or writes and reads. Thus it has been given the name ZBTTM, or Zero Bus Turnaround. The 71V3559 contains address, data-in and control signal registers. The outputs are flow-through (no output data register).