Cypress CY7C1563V18, CY7C1565V18, CY7C1561V18, CY7C1576V18 User Manual

72-Mbit QDR™-II+ SRAM 4-Word Burst
Architecture (2.5 Cycle Read Latency)
CY7C1561V18, CY7C1576V18 CY7C1563V18, CY7C1565V18

Features

Note
1. The QDR consortium specification for V
DDQ
is 1.5V + 0.1V. The Cypress QDR devices exceed the QDR consortium specification and are capable of supporting
V
DDQ
= 1.4V to VDD.

Configurations

Separate independent read and write data portsSupports concurrent transactions
400 MHz clock for high bandwidth
4-word burst for reducing address bus frequency
Double Data Rate (DDR) interfaces on both read and write ports
(data transferred at 800 MHz) at 400 MHz
Available in 2.5 clock cycle latency
Two input clocks (K and K) for precise DDR timingSRAM uses rising edges only
Echo clocks (CQ and CQ) simplify data capture in high-speed
systems
Data valid pin (QVLD) to indicate valid data on the output
Single multiplexed address input bus latches address inputs
for both read and write ports
Separate port selects for depth expansion
Synchronous internally self-timed writes
Available in x8, x9, x18, and x36 configurations
Full data coherency, providing most current data
Core V
HSTL inputs and variable drive HSTL output buffers
Available in 165-Ball FBGA package (15 x 17 x 1.4 mm)
Offered in both Pb-free and non Pb-free packages
JTAG 1149.1 compatible test access port
Delay Lock Loop (DLL) for accurate data placement
= 1.8V ± 0.1V; IO V
DD
= 1.4V to V
DDQ
DD
[1]
With Read Cycle Latency of 2.5 cycles:
CY7C1561V18 – 8M x 8 CY7C1576V18 – 8M x 9 CY7C1563V18 – 4M x 18 CY7C1565V18 – 2M x 36

Functional Description

The CY7C1561V18, CY7C1576V18, CY7C1563V18, and CY7C1565V18 are 1.8V Synchronous Pipelined SRAMs, equipped with QDR-II+ architecture. Similar to QDR-II archi­tecture, QDR-II+ SRAMs consists of two separate ports: the read port and the write port to access the memory array. The read port has dedicated data outputs to support read operations and the write port has dedicated data inputs to support write operations. QDR-II+ architecture has separate data inputs and data outputs to completely eliminate the need to “turn-around” the data bus that exists with common IO devices. Each port is accessed through a common address bus. Addresses for read and write addresses are latched on alternate rising edges of the input (K) clock. Accesses to the QDR-II+ read and write ports are completely independent of one another. To maximize data throughput, both read and write ports are equipped with DDR interfaces. Each address location is associated with four 8-bit words (CY7C1561V18), 9-bit words (CY7C1576V18), 18-bit words (CY7C1563V18), or 36-bit words (CY7C1565V18) that burst sequentially into or out of the device. Because data is trans­ferred into and out of the device on every rising edge of both input clocks (K and K fying system design by eliminating bus “turn-arounds”.
Depth expansion is accomplished with port selects, which enables each port to operate independently.
All synchronous inputs pass through input registers controlled by the K or K registers controlled by the K or K conducted with on-chip synchronous self-timed write circuitry.
), memory bandwidth is maximized while simpli-
input clocks. All data outputs pass through output
input clocks. Writes are

Selection Guide

Maximum Operating Frequency 400 375 333 300 MHz Maximum Operating Current x8 1400 1300 1200 1100 mA
Cypress Semiconductor Corporation 198 Champion Court San Jose, CA 95134-1709 408-943-2600 Document Number: 001-05384 Rev. *F Revised March 6, 2008
Description 400 MHz 375 MHz 333 MHz 300 MHz Unit
x9 1400 1300 1200 1100 x18 1400 1300 1200 1100 x36 1400 1300 1200 1100
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CY7C1561V18, CY7C1576V18 CY7C1563V18, CY7C1565V18

Logic Block Diagram (CY7C1561V18)

2M x 8 Array
CLK
A
(20:0)
Gen.
K
K
Control
Logic
Address Register
D
[7:0]
Read Add. Decode
Read Data Reg.
RPS
WPS
Control
Logic
Address Register
Reg.
Reg.
Reg.
16
21
32
8
NWS
[1:0]
V
REF
Write Add. Decode
Write
Reg
16
A
(20:0)
21
2M x 8 Array
2M x 8 Array
2M x 8 Array
8
CQ
CQ
DOFF
Q
[7:0]
8
QVLD
8
8
8
Write
Reg
Write
Reg
Write
Reg
2M x 9 Array
CLK
A
(20:0)
Gen.
K
K
Control
Logic
Address Register
D
[8:0]
Read Add. Decode
Read Data Reg.
RPS
WPS
Control
Logic
Address Register
Reg.
Reg.
Reg.
18
21
36
9
BWS
[0]
V
REF
Write Add. Decode
Write
Reg
18
A
(20:0)
21
2M x 9 Array
2M x 9 Array
2M x 9 Array
9
CQ
CQ
DOFF
Q
[8:0]
9
QVLD
9
9
9
Write
Reg
Write
Reg
Write
Reg

Logic Block Diagram (CY7C1576V18)

Document Number: 001-05384 Rev. *F Page 2 of 28
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Logic Block Diagram (CY7C1563V18)

1M x 18 Array
CLK
A
(19:0)
Gen.
K
K
Control
Logic
Address Register
D
[17:0]
Read Add. Decode
Read Data Reg.
RPS
WPS
Control
Logic
Address
Register
Reg.
Reg.
Reg.
36
20
72
18
BWS
[1:0]
V
REF
Write Add. Decode
Write
Reg
36
A
(19:0)
20
1M x 18 Array
1M x 18 Array
1M x 18 Array
18
CQ
CQ
DOFF
Q
[17:0]
18
QVLD
18
18
18
Write
Reg
Write
Reg
Write
Reg
512K x 36 Array
CLK
A
(18:0)
Gen.
K
K
Control
Logic
Address Register
D
[35:0]
Read Add. Decode
Read Data Reg.
RPS
WPS
Control
Logic
Address Register
Reg.
Reg.
Reg.
72
19
144
36
BWS
[3:0]
V
REF
Write Add. Decode
Write
Reg
72
A
(18:0)
19
512K x 36 Array
512K x 36 Array
512K x 36 Array
36
CQ
CQ
DOFF
Q
[35:0]
36
QVLD
36
36
36
Write
Reg
Write
Reg
Write
Reg

Logic Block Diagram (CY7C1565V18)

Document Number: 001-05384 Rev. *F Page 3 of 28
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Pin Configuration

Note
2. NC/144M and NC/288M are not connected to the die and can be tied to any voltage level.
The pin configuration for CY7C1561V18, CY7C1576V18, CY7C1563V18, and CY7C1565V18 follow.

165-Ball FBGA (15 x 17 x 1.4 mm) Pinout

CY7C1561V18 (8M x 8)
1 2 3 4 5 6 7 8 9 10 11
A CQ AAWPSNWS
1
B NC NC NC A NC/288M K NWS C NC NC NC V D NC D4 NC V E NC NC Q4 V F NC NC NC V G NC D5 Q5 V H DOFF V
REF
V
DDQ
V
J NC NC NC V K NC NC NC V L NC Q6 D6 V M NC NC NC V N NC D7 NC V
SS
SS DDQ DDQ DDQ DDQ DDQ DDQ DDQ
SS
SS
ANCAVSSNC NC D3
V
SS
V
SS
V
DD
V
DD
V
DD
V
DD
V
DD
V
SS
V
SS
AAAVSSNC NC NC
P NC NC Q7 A A QVLD A A NC NC NC R TDOTCKAAANCAAATMSTDI
K NC/144M RPS AACQ
0
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
DD
V
DD
V
DD
V
DD
V
DD
V
SS
V
SS
ANCNCQ3
V
SS
V
DDQ
V
DDQ
V
DDQ
V
DDQ
V
DDQ
V
DDQ
V
DDQ
V
SS
[2]
NC NC NC NC D2 Q2 NC NC NC NC NC NC
V
DDQ
V
REF
NC Q1 D1 NC NC NC NC NC Q0 NC NC D0
ZQ
CY7C1576V18 (8M x 9)
1 2 3 4 5 6 7 8 9 10 11
A CQ AAWPSNC K NC/144M RPS AACQ B NC NC NC A NC/288M K BWS C NC NC NC V D NC D5 NC V E NC NC Q5 V F NC NC NC V G NC D6 Q6 V H DOFF V
REF
V
DDQ
V
J NC NC NC V K NC NC NC V L NC Q7 D7 V M NC NC NC V N NC D8 NC V
SS
SS DDQ DDQ DDQ DDQ DDQ DDQ DDQ
SS
SS
ANCAVSSNC NC D4
V
SS
V
SS
V
DD
V
DD
V
DD
V
DD
V
DD
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
DD
V
DD
V
DD
V
DD
V
DD
V
SS
V
SS
AAAVSSNC NC NC
0
ANCNCQ4
V V V V V V V
V
DDQ DDQ DDQ DDQ DDQ DDQ DDQ
V
SS
SS
NC NC NC NC D3 Q3 NC NC NC NC NC NC
V
DDQ
V
REF
NC Q2 D2 NC NC NC NC NC Q1 NC NC D1
ZQ
P NC NC Q8 A A QVLD A A NC D0 Q0 R TDOTCKAAANCAAATMSTDI
Document Number: 001-05384 Rev. *F Page 4 of 28
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Pin Configuration (continued)
The pin configuration for CY7C1561V18, CY7C1576V18, CY7C1563V18, and CY7C1565V18 follow.
165-Ball FBGA (15 x 17 x 1.4 mm) Pinout
CY7C1563V18 (4M x 18)
1 2 3 4 5 6 7 8 9 10 11
A CQ NC/144M A WPS BWS
1
B NC Q9 D9 A NC K BWS C NC NC D10 V D NC D11 Q10 V E NC NC Q11 V F NC Q12 D12 V G NC D13 Q13 V H DOFF V
REF
V
DDQ
V
J NC NC D14 V K NC NC Q14 V L NC Q15 D15 V M NC NC D16 V N NC D17 Q16 V
SS
SS DDQ DDQ DDQ DDQ DDQ DDQ DDQ
SS
SS
ANCAVSSNC Q7 D8
V
SS
V
SS
V
DD
V
DD
V
DD
V
DD
V
DD
V
SS
V
SS
AAAVSSNC NC D1
P NC NC Q17 A A QVLD A A NC D0 Q0 R TDOTCKAAANCAAATMSTDI
K NC/288M RPS AACQ
0
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
DD
V
DD
V
DD
V
DD
V
DD
V
SS
V
SS
ANCNCQ8
V
SS
V
DDQ
V
DDQ
V
DDQ
V
DDQ
V
DDQ
V
DDQ
V
DDQ
V
SS
[2]
NC NC D7 NC D6 Q6 NC NC Q5 NC NC D5
V
DDQ
V
REF
NC Q4 D4 NC D3 Q3 NC NC Q2 NC Q1 D2
ZQ
CY7C1565V18 (2M x 36)
1 2 3 4 5 6 7 8 9 10 11
A CQ NC/288M A WPS BWS B Q27 Q18 D18 A BWS C D27 Q28 D19 V D D28 D20 Q19 V E Q29 D29 Q20 V F Q30 Q21 D21 V G D30 D22 Q22 V H DOFF V
REF
V
DDQ
V
J D31 Q31 D23 V K Q32 D32 Q23 V L Q33 Q24 D24 V M D33 Q34 D25 V N D34 D26 Q25 V
SS
SS DDQ DDQ DDQ DDQ DDQ DDQ DDQ
SS
SS
ANCAVSSD16 Q7 D8
V
SS
V
SS
V
DD
V
DD
V
DD
V
DD
V
DD
V
SS
V
SS
AAAVSSQ10 D9 D1
2 3
K BWS
RPS A NC/144M CQ
1
KBWS0AD17Q17Q8
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
SS
V
DD
V
DD
V
DD
V
DD
V
DD
V
SS
V
SS
V V V V V V V
V
DDQ DDQ DDQ DDQ DDQ DDQ DDQ
V
SS
SS
Q16 D15 D7 Q15 D6 Q6 D14 Q14 Q5 Q13 D13 D5
V
DDQ
V
REF
D12 Q4 D4 Q12 D3 Q3 D11 Q11 Q2 D10 Q1 D2
ZQ
P Q35 D35 Q26 A A QVLD A A Q9 D0 Q0 R TDOTCKAAANCAAATMSTDI
Document Number: 001-05384 Rev. *F Page 5 of 28
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Pin Definitions

Pin Name IO Pin Description
D
[x:0]
Input-
Synchronous
WPS Input-
Synchronous
NWS NWS1,
BWS BWS BWS BWS
,
0
,
0
,
1
,
2 3
Input-
Synchronous
Input-
Synchronous
A Input-
Synchronous
Q
[x:0]
Outputs-
Synchronous
RPS Input-
Synchronous
Data Input Signals. Sampled on the rising edge of K and K clocks when valid write operations are active. CY7C1561V18 D CY7C1576V18 D
CY7C1563V18 D CY7C1565V18 D
[7:0] [8:0] [17:0] [35:0]
Write Port Select Active LOW. Sampled on the rising edge of the K clock. When asserted active, a write operation is initiated. Deasserting deselects the Write Port. Deselecting the write port ignores D
[x:0]
Nibble Write Select 0, 1 Active LOW (CY7C1561V18 Only). Sampled on the rising edge of the K and K
clocks when write operations are active. Used to select which nibble is written into the device during the current portion of the write operations. NWS All the Nibble Write Selects are sampled on the same edge as the data. Deselecting a Nibble Write Select
controls D
0
and NWS1 controls D
[3:0]
[7:4]
.
ignores the corresponding nibble of data and it is not written into the device. Byte Write Select 0, 1, 2, and 3 Active LOW . Sampled on the rising edge of the K and K clocks when
write operations are active. Used to select which byte is written into the device during the current portion of the write operations. Bytes not written remain unaltered. CY7C1576V18 BWS CY7C1563V18 BWS0 controls D CY7C1565V18 BWS0 controls D BWS
controls D
2
All the Byte Write Selects are sampled on the same edge as the data. Deselecting a Byte Write Select
controls D
0
and BWS3 controls D
[26:18]
[8:0]
and BWS1 controls D
[8:0]
, BWS1 controls D
[8:0]
[35:27].
[17:9]
[17:9].
,
ignores the corresponding byte of data and it is not written into the device. Address Inputs. Sampled on the rising edge of the K clock during active read and write operations. These
address inputs are multiplexed for both read and write operations. Internally, the device is organized as 8M x 8 (4 arrays each of 2M x 8) for CY7C1561V18, 8M x 9 (4 arrays each of 2M x 9) for CY7C1576V18, 4M x 18 (4 arrays each of 1M x 18) for CY7C1563V18 and 2M x 36 (4 arrays each of 512K x 36) for CY7C1565V18. Therefore, only 21 address inputs are needed to access the entire memory array of CY7C1561V18 and CY7C1576V18, 20 address inputs for CY7C1563V18, and 19 address inputs for CY7C1565V18. These inputs are ignored when the appropriate port is deselected.
Data Output Signals. These pins drive out the requested data during a read operation. Valid data is driven out on the rising edge of both the K and K port, Q CY7C1561V18 Q CY7C1576V18 Q CY7C1563V18 Q CY7C1565V18 Q
are automatically tri-stated.
[x:0]
[7:0] [8:0] [17:0] [35:0]
clocks during read operations. On deselecting the read
Read Port Select Active LOW. Sampled on the rising edge of positive input clock (K). When active, a read operation is initiated. Deasserting deselects the read port. When deselected, the pending access is allowed to complete and the output drivers are automatically tri-stated following the next rising edge of the K
clock. Each read access consists of a burst of four sequential transfers.
.
QVLD Valid output
Valid Outp ut Indicator. The Q Valid indicates valid output data. QVLD is edge aligned with CQ and CQ
indicator
K Input-
Clock
K
Input­Clock
Positive Input Clock Input. The rising edge of K is used to capture synchronous inputs to the device and to drive out data through Q
. All accesses are initiated on the risin g ed ge of K.
[x:0]
Negative Input Clock Input. K is used to capture synchronous inputs being presented to the device and to drive out data through Q
[x:0]
.
CQ Echo Clock Synchronous Echo Clock Outputs. This is a free running clock and is synchronized to the input clock
(K) of the QDR-II+. The timings for the echo clocks are shown in the Switching Characteristics on page 23.
CQ
Echo Clock Synchronous Echo Clock Outputs . This is a free running clock and is synchronized to the input clock
(K
) of the QDR-II+. The timings for the echo clocks are shown in the Switching Characteristics on page 23.
Document Number: 001-05384 Rev. *F Page 6 of 28
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Pin Definitions (continued)
Pin Name IO Pin Description
ZQ Input Output Impedance Matching Input. This input is used to tune the device outputs to the system data bus
impedance. CQ, CQ between ZQ and ground. Alternately, this pin can be connected directly to V minimum impedance mode. This pin cannot be connected directly to GND or left unconnected.
DOFF Input DLL Turn Off Active LOW. Connecting this pin to ground turns off the DLL inside the device.The timings
in the DLL turned off operation are different from those listed in this data sheet. For normal operation, this pin can be connected to a pull up through a 10 KΩ or less pull up resistor. The device behaves in QDR-I mode when the DLL is turned off. In this mode, the device can b e operated at a frequency o f up to 167 MHz with QDR-I timing.
TDO Output TDO for JTAG. TCK Input TCK Pin for JTAG. TDI Input TDI Pin for JTAG. TMS Input TMS Pin for JTAG. NC N/A Not Connected to the Die. Can be tied to any voltage level.
NC/144M N/A Not Connected to the Die. Can be tied to any voltage level. NC/288M N/A Not Connected to the Die. Can be tied to any voltage level.
and Q
output impedance are set to 0.2 x RQ, where RQ is a resistor connected
[x:0]
, which enables the
DDQ
V
V V V
REF
DD SS DDQ
Input-
Reference
Power Supply Power Supply Inputs to the Core of the Device.
Ground Ground for the Device.
Power Supply Power Supply Inputs for the Outputs of the Device.
Reference Voltage Input. Static input used to set the reference level for HSTL inputs and Outputs as well as AC measurement points.
Document Number: 001-05384 Rev. *F Page 7 of 28
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Functional Overview

The CY7C1561V18, CY7C1576V18, CY7C1563V18, and CY7C1565V18 are synchronous pipelined Burst SRAMs equipped 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 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 CY7C1561V18, four 9-bit data transfers in the case of CY7C1576V18, four 18-bit data transfers in the case of CY7C1563V18, and four 36-bit data transfers in the case of CY7C1565V18, in two clock cycles.
Accesses for both ports are initiated on the positive input clock (K). All synchronous input and output timing are referenced from the rising edge of the input clocks (K and K
All synchronous data inputs (D registers controlled by the input clocks (K and K synchronous data outputs (Q registers controlled by the rising edge of the input clocks (K and
[x:0]
) outputs pass through output
[x:0]
K) as well. All synchronous control (RPS
, WPS, NWS pass through input registers controlled by the rising edge of the input clocks (K and K
).
CY7C1563V18 is described in the following sections. The same basic descriptions apply to CY7C1561V18, CY7C1576V18, and CY7C1565V18.

Read Operations

The CY7C1563V18 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 address inputs are stored in the read address register. Following the next two K sponding lowest order 18-bit word of data is driven onto the
using K as the output timing reference. On the su bse-
Q
[17:0]
quent rising edge of K, the next 18-bit data word is driven onto the Q have been driven out onto Q
0.45 ns from the rising edge of the input clock (K or K 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 input clocks (K and K
When the read port is deselected, the CY7C1563V18 first completes the pending read transactions. Synchronous internal circuitry automatically tri-states the outputs following the next rising edge of the negative input clock (K
. This process continues until all four 18-bit data words
[17:0]
. The requested data is valid
[17:0]
).
).
) inputs pass through input
). All
[x:0]
, BWS
[x:0]
) inputs
clock rise, the corre-
). To
). This enables for 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 the lower 18-bit write data register, provided BWS asserted active. On the subsequent rising edge of the negative input clock (K) the information presented to D into the write data register, provided BWS active. This process continues for one more cycle until four 18-bit
is latched and stored into
[17:0]
[1:0]
is also stored
[17:0]
are both asserted
[1:0]
are both
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 have been completed.

Byte Write Operations

Byte write operations are supported by the CY7C1563V18. A write operation is initiated as described in the Write Operations section. The bytes that are written are determined by BWS
, which are sampled with each set of 18-bit data words.
BWS
1
Asserting the appropriate Byte Write Select input during the data
and
0
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.

Concurrent Transactions

The read and write ports on the CY7C1563V18 operates completely 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 includes forwarding data from a write cycle that was initiated on the previous K clock rise.
Read access and write access must be scheduled such that one transaction is initiated on any clock cycle. If both ports are selected on the same K clock rise, the arbitration depends on the previous state of the SRAM. If both ports are deselected, the read port takes priority. If a read was initiated on the previous cycle, the write port takes priority (as read operations cannot be initiated on consecutive cycles). If a write was initiated on the previous cycle, the read port takes priority (since write operations cannot be initiated on consecutive cycles). Therefore, asserting both port selects active from a deselected state results in alter­nating read or write operations being initiated, with the first access being a read.
Document Number: 001-05384 Rev. *F Page 8 of 28
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Depth Expansion

The CY7C1563V18 has a port select input for each port. This enables for easy depth expansion. Both port selects are sampled on the rising edge of the positive input clock only (K). Each port select input can deselect the specified port. Deselecting a port does not affect the other port. All pending transactions (read and write) are completed prior to the device being deselected.

Programmable Impedance

An external resistor, RQ, must be connected between the ZQ pin on the SRAM and V driver impedance. The value of RQ must be 5X the value of the
to allow the SRAM to adjust its output
SS
intended line impedance driven by the SRAM, the allowable range of RQ to guarantee impedance matching with a tolerance of ±15% is between 175Ω and 350Ω output impedance is adjusted every 1024 cycles upon power up
, with V
=1.5V. The
DDQ
to account for drifts in supply voltage and temperature.

Echo Clocks

Echo clocks are provided on the QDR-II+ to simplify data capture on high-speed systems. Two echo clocks are generated by the QDR-II+. CQ is referenced with respect to K and CQ is refer­enced with respect to K
. These are free-running clocks and are synchronized to the input clock of the QDR-II+. The timing for the echo clocks are shown in Switching Characteristics on page 23.

Application Example

Valid Data Indicator (QVLD)

QVLD is provided on the QDR-II+ to simplify data capture on high speed systems. The QVLD is generated by the QDR-II+ device along with data output. This signal is also edge-aligned with the echo clock and follows the timing of any data pin. This signal is asserted half a cycle before valid data arrives.
DLL
These chips use a Delay Lock Loop (DLL) that is designed to function between 120 MHz and the specified maximum clock frequency. The DLL may be disabled by applying ground to the DOFF pin. When the DLL is turned off, the device behaves in QDR-I mode (with 1.0 cycle latency and a longer access time ). For more information, refer to the application note, “DLL Consid­erations in QDRII/DDRII/QDRII+/DDRII+”. The DLL can also be reset by slowing or stopping the input clocks K and K minimum of 30ns. However, it is not necessary to reset the DLL to lock to the desired frequency. During Power up, when the DOFF
is tied HIGH, the DLL is locked after 2048 cycles of stable
clock.
for a
Figure 1 shows four QDR-II+ used in an application.
Figure 1. Application Example
SRAM #1
D
WPS
RPS
A
DATA OUT
BUS MASTER
(CPU or ASIC)
CLKIN/CLKIN
Vt
R
DATA IN
Address
RPS WPS BWS
Source K Source K
BWS
ZQ
CQ/CQ
K
RQ = 250ohms
Q
K
D A
SRAM #4
WPS
RPS
R
Vt
Vt
R
R = 50ohms, Vt = V /2
BWS
ZQ
CQ/CQ
K
DDQ
RQ = 250ohms
Q
K
Document Number: 001-05384 Rev. *F Page 9 of 28
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