CY7C138V

The CY7C138V/144V/006V/007V and CY7C139V/145V/016V/017V are low-power CMOS 4K, 8K, 16K, and 32K x8/9 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 are provided, permitting independent, asynchronous access for reads and writes to any location in memory. The devices can be utilized as standalone 8/9-bit dual-port static RAMs or multiple devices can be combined in order to function as a 16/18-bit or wider master/slave dual-port static RAM. An M/S pin is provided for implementing 16/18-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 of CY7C138AV/144AV/006AV/007AV and CY7C139AV/145AV/ 016AV/017AV has independent control pins: Chip Enable (CE), 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 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 a chip select (CE) pin.