CY7C028

The CY7C027/028 and CY7C037/038 are low-power CMOS 32K, 64K x 16/18 dual-port static RAMs. Various arbitration schemes are included on the devices to handle situations when multiple processors access the same piece of data. Two ports of CY7C028 are provided, permitting independent, asynchronous access for reads and writes to any location in memory. The devices can be utilized as standalone 16/18-bit dual-port static RAMs or multiple devices can be combined in order to function of CY7C028 as a 32/36-bit or wider master/slave dual-port static RAM. An M/S pin of CY7C028 is provided for implementing 32/36-bit or wider memory applications without the need for separate master and slave devices or additional discrete logic. Application areas include interprocessor/multiprocessor designs, communications status buffering, and dual-port video/graphics memory.

Each port has independent control pins of CY7C028: dual chip enables (CE₀ and CE₁), read or write enable (R/W), and output enable (OE). Two flags are provided on each port (BUSY and INT). BUSY signals that the port is trying to access the same location currently being accessed by the other port. The interrupt flag (INT) permits communication between ports or systems by means of a mail box. The semaphores of CY7C028 are used to pass a flag, or token, from one port to the other to indicate that a shared resource is in use. The semaphore logic is comprised of eight shared latches. Only one side can control the latch (semaphore) at any time. Control of a semaphore indicates that a shared resource is in use. An automatic power-down feature is controlled independently on each port by the chip enable pins.

The CY7C027/028 and CY7C037/038 are available in 100-pin Thin Quad Plastic Flatpack (TQFP) packages.