The CY7C4261/71/81/91V are high-speed, low-power FIFO memories with clocked read and write interfaces. All are nine bits wide. The CY7C4261/71/81/91V are pin-compatible to the CY7C42x1V Synchronous FIFO family. Programmable features include Almost Full/Almost Empty flags. These FIFOs provide solutions for a wide variety of data buffering needs, including high-speed data acquisition, multiprocessor inter­faces, and communications buffering.

These FIFOs have 9-bit input and output ports that are controlled by separate clock and enable signals. The input port is controlled by a free-running clock (WCLK) and two write-enable pins (/WEN1, WEN2//LD).

When /WEN1 is LOW and WEN2//LD is HIGH, data is written into the FIFO on the rising edge of the WCLK signal. While /WEN1 and WEN2//LD are held active, data is continually written into the FIFO on each WCLK cycle. The output port is controlled in a similar manner by a free-running read clock (RCLK) and two read enable pins (/REN1, /REN2). In addition, the CY7C4261/71/81/91V has an output enable pin (/OE). The read (RCLK) and write (WCLK) clocks may be tied together for single-clock operation or the two clocks may be run indepen­dently for asynchronous read/write applications. Clock frequencies up to 100 MHz are achievable. Depth expansion is possible using one enable input for system control, while the other enable is controlled by expansion logic to direct the flow of data.