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IDT71P74604 डेटा पत्रक PDF( Datasheet डाउनलोड )


डेटा पत्रक - (IDT71P74x04) 18Mb Pipelined QDR II SRAM Burst of 4 - IDT

भाग संख्या IDT71P74604
समारोह (IDT71P74x04) 18Mb Pipelined QDR II SRAM Burst of 4
मैन्युफैक्चरर्स IDT 
लोगो IDT लोगो 
पूर्व दर्शन
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<?=IDT71P74604?> डेटा पत्रक पीडीएफ

IDT71P74604 pdf
IDT71P74204 (2M x 8-Bit), 71P74104 (2M x 9-Bit), 71P74804 (1M x 18-Bit) 71P74604 (512K x 36-Bit)
Advance Information
18 Mb QDR II SRAM Burst of 4
Commercial Temperature Range
that is precisely timed to the data output, and tuned with matching imped-
ance and signal quality. The user can use the echo clock for down-
stream clocking of the data. Echo clocks eliminate the need for the user
to produce alternate clocks with precise timing, positioning, and signal
qualities to guarantee data capture. Since the echo clocks are generated
by the same source that drives the data output, the relationship to the data
is not significantly affected by voltage, temperature and process, as would
be the case if the clock were generated by an outside source.
All interfaces of the QDRII SRAM are HSTL, allowing speeds beyond
SRAM devices that use any form of TTL interface. The interface can be
scaled to higher voltages (up to 1.9V) to interface with 1.8V systems if
necessary. The device has a VDDQ and a separate Vref, allowing the
user to designate the interface operational voltage, independent of the
device core voltage of 1.8V VDD. The output impedance control allows
the user to adjust the drive strength to adapt to a wide range of loads and
transmission lines.
The device is capable of sustaining full bandwidth on both the input
and output ports simultaneously. All data is in two word bursts, with
addressing capability to the burst level.
Clocking
The QDRII SRAM has two sets of input clocks, namely the K, K clocks
and the C, C clocks. In addition, the QDRII has an output “echo” clock,
CQ, CQ.
The K and K clocks are the primary device input clocks. The K clock
is, used to clock in the control signals (R, W and BWx/NWx), the ad-
dress, first and third words of the data burst during a write operation.
The K clock is used to clock in the control signals (BWx or NWx) and the
second and fourth words of the data burst during a write operation. The
K and K clocks are also used internally by the SRAM. In the event that
the user disables the C and C clocks, the K and K clocks will be used to
clock the data out of the output register and generate the echo clocks.
The C and C clocks may be used to clock the data out of the output
register during read operations and to generate the echo clocks. C and
C must be presented to the SRAM within the timing tolerances. The
output data from the QDRII will be closely aligned to the C and C input,
through the use of an internal DLL. When C is presented to the QDRII
SRAM, the DLL will have already internally clocked the data to arrive at
the device output simultaneously with the arrival of the C clock. The C
and second data item of the burst will also correspond. The third and
fourth data items will follow on the next clock cycle.
Single Clock Mode
The QDRII SRAM may be operated with a single clock pair. C and C
may be disabled by tying both signals high, forcing the outputs and echo
clocks to be controlled instead by the K and K clocks.
DLL Operation
The DLL in the output structure of the QDRII SRAM can be used to
closely align the incoming clocks C and C with the output of the data,
generating very tight tolerances between the two. The user may disable
the DLL by holding Doff low. With the DLL off, the C and C (or K and K
if C and C are not used) will directly clock the output register of the SRAM.
With the DLL off, there will be a propagation delay from the time the clock
enters the device until the data appears at the output.
Echo Clock
The echo clocks, CQ and CQ, are generated by the C and C clocks
(or K, K if C, C are disabled). The rising edge of C generates the rising
edge of CQ, and the falling edge of CQ. The rising edge of C generates
the rising edge of CQ and the falling edge of CQ. This scheme improves
the correlation of the rising and falling edges of the echo clock and will
improve the duty cycle of the individual signals.
The echo clock is very closely aligned with the data, guaranteeing that
the echo clock will remain closely correlated with the data, within the
tolerances designated.
Read and Write Operations
QDRII devices internally store the 4 words of the burst as a single,
wide word and will retain their order in the burst. There is no ability to
address to the single word level or reverse the burst order; however, the
byte and nibble write signals can be used to prevent writing any indi-
vidual bytes, or combined to prevent writing one word of the burst.
Read and write operations may be interleaved with each occurring
on every other clock cycle. In the event that two reads or two writes are
requested on adjacent clock cycles, the operation in progress will com-
plete and the second request will be ignored. In the event that both a
read and write are requested simultaneously, the read operation will win
and the write operation will be ignored.
Read operations are initiated by holding the read port select (R) low,
and presenting the read address to the address port during the rising
edge of K which will latch the address. The data will then be read and will
appear at the device output at the designated time in correspondence
with the C and C clocks.
Write operations are initiated by holding the write port select (W) low
and presenting the designated write address to the address bus. The
QDRII SRAM will receive the address on the rising edge of clock K. On
the following rising edge of K clock, the QDRII SRAM will receive the first
data item of the four word burst on the data bus. Along with the data, the
byte (BW) or nibble write (NW) inputs will be accepted, indicating which
bytes of the data inputs should be written to the SRAM. On the rising
edge of K, the next word of the write burst and BW/NW will be accepted.
The following K and K will receive the last two words of the four word
burst, with their BW/NW enables.
Output Enables
The QDRII SRAM automatically enables and disables the Q[X:0]
outputs. When a valid read is in progress, and data is present at the
output, the output will be enabled. If no valid data is present at the output
(read not active), the output will be disabled (high impedance). The
echo clocks will remain valid at all times and cannot be disabled or turned
off. During power-up the Q outputs will come up in a high impedance
state.
Programmable Impedance
An external resistor, RQ, must be connected between the ZQ pin on
the SRAM and Vss to allow the SRAM to adjust its output drive imped-
ance. The value of RQ must be 5X the value of the intended drive
impedance of the SRAM. The allowable range of RQ to guarantee
impedance matching with a tolerance of +/- 10% is between 175 ohms
and 350 ohms, with VDDQ = 1.5V. The output impedance is adjusted
every 1024 clock cycles to correct for drifts in supply voltage and tem-
perature. If the user wishes to drive the output impedance of the SRAM
to it’s lowest value, the ZQ pin may be tied to VDDQ.
6.242

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भाग संख्याविवरणविनिर्माण
IDT71P74604(IDT71P74x04) 18Mb Pipelined QDR II SRAM Burst of 4IDT
IDT


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