Cypress Perform CY7C1413BV18 - Manual (Page 8)

CY7C1411BV18, CY7C1426BV18
CY7C1413BV18, CY7C1415BV18
Document Number: 001-07037 Rev. *D Page 8 of 30
Functional Overview
The CY7C1411BV18, CY7C1426BV18, CY7C1413BV18 and
CY7C1415BV18 are synchronous pipelined burst SRAMs with a
read port and a write port. The read port is dedicated to read
operations and the write port is dedicated to write operations.
Data flows into the SRAM through the write port and flows out
through the read port. These devices multiplex the address
inputs to minimize the number of address pins required. By
having separate read and write ports, the QDR-II completely
eliminates the need to turn-around the data bus and avoids any
possible data contention, thereby simplifying system design.
Each access consists of four 8-bit data transfers in the case of
CY7C1411BV18, four 9-bit data transfers in the case of
CY7C1426BV18, four 18-bit data transfers in the case of
CY7C1413BV18, and four 36-bit transfers data in the case of
CY7C1415BV18 in two clock cycles.
This device operates with a read latency of one and half cycles
when DOFF pin is tied HIGH. When DOFF pin is set LOW or
connected to V
SS
then device behaves in QDR-I mode with a
read latency of one clock cycle.
Accesses for both ports are initiated on the positive input clock
(K). All synchronous input timing is referenced from the rising
edge of the input clocks (K and K) and all output timing is refer-
enced to the output clocks (C and C or K and K when in single
clock mode).
All synchronous data inputs (D
[x:0]
) pass through input registers
controlled by the input clocks (K and K). All synchronous data
outputs (Q
[x:0]
) pass through output registers controlled by the
rising edge of the output clocks (C and C or K and K when in
single clock mode).
All synchronous control (RPS, WPS, BWS
[x:0]
) inputs pass
through input registers controlled by the rising edge of the input
clocks (K and K).
CY7C1413BV18 is described in the following sections. The
same basic descriptions apply to CY7C1411BV18,
CY7C1426BV18, and CY7C1415BV18.
Read Operations
The CY7C1413BV18 is organized internally as four arrays of
512K x 18. Accesses are completed in a burst of four sequential
18-bit data words. Read operations are initiated by asserting
RPS
active at the rising edge of the positive input clock (K). The
address presented to address inputs are stored in the read
address register. Following the next K clock rise, the corre-
sponding lowest order 18-bit word of data is driven onto the
Q
[17:0]
using C as the output timing reference. On the subse-
quent rising edge of C, the next 18-bit data word is driven onto
the Q
[17:0]
. This process continues until all four 18-bit data words
have been driven out onto Q
[17:0]
. The requested data is valid
0.45 ns from the rising edge of the output clock (C or C, or K or
K when in single clock mode). To maintain the internal logic, each
read access must be allowed to complete. Each read access
consists of four 18-bit data words and takes two clock cycles to
complete. Therefore, read accesses to the device can not be
initiated on two consecutive K clock rises. The internal logic of
the device ignores the second read request. Read accesses can
be initiated on every other K clock rise. Doing so pipelines the
data flow such that data is transferred out of the device on every
rising edge of the output clocks (C and C, or K and K when in
single clock mode).
When the read port is deselected, the CY7C1413BV18 first
completes the pending read transactions. Synchronous internal
circuitry automatically tri-states the outputs following the next
rising edge of the positive output clock (C). This enables for a
transition between devices without the insertion of wait states in
a depth expanded memory.
Write Operations
Write operations are initiated by asserting WPS active at the
rising edge of the positive input clock (K). On the following K
clock rise the data presented to D
[17:0]
is latched and stored into
the lower 18-bit write data register, provided BWS
[1:0]
are both
asserted active. On the subsequent rising edge of the negative
input clock (K), the information presented to D
[17:0]
is also stored
into the write data register, provided BWS
[1:0]
are both asserted
active. This process continues for one more cycle until four 18-bit
words (a total of 72 bits) of data are stored in the SRAM. The 72
bits of data are then written into the memory array at the specified
location. Therefore, write accesses to the device can not be
initiated on two consecutive K clock rises. The internal logic of
the device ignores the second write request. Initiate write access
on every other rising edge of the positive input clock (K). Doing
so pipelines the data flow such that 18 bits of data transfers into
the device on every rising edge of the input clocks (K and K).
When deselected, the write port ignores all inputs after the
pending write operations have been completed.
Byte Write Operations
Byte write operations are supported by the CY7C1413BV18. A
write operation is initiated as described in the
Write Operations
section. The bytes that are written are determined by BWS
0
and
BWS
1
, which are sampled with each set of 18-bit data words.
Asserting the appropriate Byte Write Select input during the data
portion of a write latches the data being presented and writes it
into the device. Deasserting the Byte Write Select input during
the data portion of a write enables the data stored in the device
for that byte to remain unaltered. This feature can be used to
simplify read, modify, or write operations to a byte write
operation.
Single Clock Mode
The CY7C1411BV18 can be used with a single clock that
controls both the input and output registers. In this mode the
device recognizes only a single pair of input clock (K and K) that
control both the input and output registers. This operation is
identical to the operation if the device had zero skew between
the K/K and C/C clocks. All timing parameters remains the same
in this mode. To use this mode of operation, the user must tie C
and C HIGH at power on. This function is a strap option and not
alterable during device operation.
Concurrent Transactions
The read and write ports on the CY7C1413BV18 operates
independently of one another. As each port latches the address
inputs on different clock edges, the user can read or write to any
location, regardless of the transaction on the other port. If the
ports access the same location when a read follows a write in
successive clock cycles, the SRAM delivers the most recent
information associated with the specified address location. This
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