The 18Mb IS61DDSB251236C and IS61DDSB21M18C are synchronous, high-performance CMOS static random access memory (SRAM) devices. These SRAMs have a separate I/O bus. The rising edge of K clock initiates the read/write operation, and all internal operations are self-timed. Refer to the Timing Reference Diagram for Truth Table for a description of the basic operations of these DDR-II (Burst of 2) SIO SRAMs.