Cypress Perform CY7C1513KV18 - Manual (Page 8)

CY7C1511KV18, CY7C1526KV18
CY7C1513KV18, CY7C1515KV18
Document Number: 001-00435 Rev. *E Page 8 of 31
Functional Overview
The CY7C1511KV18, CY7C1526KV18, CY7C1513KV18,
CY7C1515KV18 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
CY7C1511KV18, four 9-bit data transfers in the case of
CY7C1526KV18, four 18-bit data transfers in the case of
CY7C1513KV18, and four 36-bit data transfers in the case of
CY7C1515KV18 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).
CY7C1513KV18 is described in the following sections. The
same basic descriptions apply to CY7C1511KV18,
CY7C1526KV18 and CY7C1515KV18.
Read Operations
The CY7C1513KV18 is organized internally as four arrays of 1M
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 the address inputs is 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
are 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 cannot 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 CY7C1513KV18 first
completes the pending read transactions. Synchronous internal
circuitry automatically tristates the outputs following the next
rising edge of the positive output clock (C). This enables a
seamless 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 cannot be
initiated on two consecutive K clock rises. The internal logic of
the device ignores the second write request. Write accesses can
be initiated on every other rising edge of the positive input clock
(K). Doing so pipelines the data flow such that 18 bits of data can
be transferred 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 are completed.
Byte Write Operations
Byte write operations are supported by the CY7C1513KV18. 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 is used to simplify
read, modify, or write operations to a byte write operation.
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