4K x 16/18 and 8K x 16/18 Dual-Port
Static RAM with SEM, INT, BUSY
CY7C024/0241
CY7C025/0251
Cypress Semiconductor Corporation
•
3901 North First Street
•
San Jose
, CA 95134
•
408-943-2600
Document #: 38-06035 Rev. *C
Revised November 11, 2004
Features
• True Dual-Ported memory cells which allow simulta-
neous reads of the same memory location
• 4K x 16 organization (CY7C024)
• 4K x 18 organization (CY7C0241)
• 8K x 16 organization (CY7C025)
• 8K x 18 organization (CY7C0251)
• 0.65-micron CMOS for optimum speed/power
• High-speed access: 15 ns
• Low operating power: ICC = 150 mA (typ.)
• Fully asynchronous operation
• Automatic power-down
• Expandable data bus to 32/36 bits or more using
Master/Slave chip select when using more than one
device
• On-chip arbitration logic
• Semaphores included to permit software handshaking
between ports
•INT flag for port-to-port communication
• Separate upper-byte and lower-byte control
• Pin select for Master or Slave
• Available in 84-pin Lead (Pb)-free PLCC, 84-pin PLCC,
100-pin Lead (Pb)-free TQFP, and 100-pin TQFP
Functional Description
The CY7C024/0241 and CY7C025/0251 are low-power
CMOS 4K x 16/18 and 8K x 16/18 dual-port static RAMs.
Various arbitration schemes are included on the CY7C024/
0241 and CY7C025/0251 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 CY7C024/
0241 and CY7C025/0251 can be utilized as standalone
16-/18-bit dual-port static RAMs or multiple devices can be
combined in order to function as a 32-/36-bit or wider master/
slave dual-port static RAM. An M/S pin is provided for imple-
menting 32-/36-bit or wider memory applications without the
need for separate master and slave devices or additional
discrete logic. Application areas include interprocessor/multi-
processor designs, communications status buffering, and
dual-port video/graphics memory.
Each port 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.
The CY7C024/0241 and CY7C025/0251 are available in
84-pin Lead (Pb)-free PLCCs, 84-pin PLCCs (CY7C024 and
CY7C025 only), 100-pin Lead (Pb)-free Thin Quad Plastic
Flatplack (TQFP) and 100-pin Thin Quad Plastic Flatpack.
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