CY7C1470BV25
CY7C1472BV25, CY7C1474BV25
Document #: 001-15032 Rev. *D
Page 8 of 29
Functional Overview
The CY7C1470BV25, CY7C1472BV25, and CY7C1474BV25
are synchronous-pipelined Burst NoBL SRAMs designed specif-
ically to eliminate wait states during read or write transitions. All
synchronous inputs pass through input registers controlled by
the rising edge of the clock. The clock signal is qualified with the
Clock Enable input signal (CEN). If CEN is HIGH, the clock signal
is not recognized and all internal states are maintained. All
synchronous operations are qualified with CEN. All data outputs
pass through output registers controlled by the rising edge of the
clock. Maximum access delay from the clock rise (tCO) is 3.0 ns
(250-MHz device).
Accesses can be initiated by asserting all three Chip Enables
(CE1, CE2, CE3) active at the rising edge of the clock. If CEN is
active LOW and ADV/LD is asserted LOW, the address
presented to the device is latched. The access can either be a
read or write operation, depending on the status of the Write
Enable (WE). BW[x] can be used to conduct Byte Write opera-
tions.
Write operations are qualified by the Write Enable (WE). All
writes are simplified with on-chip synchronous self-timed write
circuitry.
Three synchronous Chip Enables (CE1, CE2, CE3) and an
asynchronous Output Enable (OE) simplify depth expansion. All
operations (reads, writes, and deselects) are pipelined. ADV/LD
must be driven LOW after the device is deselected to load a new
address for the next operation.
Single Read Accesses
A read access is initiated when the following conditions are
satisfied at clock rise: (1) CEN is asserted LOW, (2) CE1, CE2,
and CE3 are ALL asserted active, (3) the input signal WE is
deasserted HIGH, and (4) ADV/LD is asserted LOW. The
address presented to the address inputs is latched into the
Address Register and presented to the memory core and control
logic. The control logic determines that a read access is in
progress and allows the requested data to propagate to the input
of the output register. At the rising edge of the next clock the
requested data is allowed to propagate through the output
register and onto the data bus within 2.6 ns (250-MHz device)
provided OE is active LOW. After the first clock of the read
access the output buffers are controlled by OE and the internal
control logic. OE must be driven LOW to drive out the requested
data. During the second clock, a subsequent operation (read,
write, or deselect) can be initiated. Deselecting the device is also
pipelined. Therefore, when the SRAM is deselected at clock rise
by one of the chip enable signals, its output tri-states following
the next clock rise.
Burst Read Accesses
The CY7C1470BV25, CY7C1472BV25, and CY7C1474BV25
have an on-chip burst counter that enables the user to supply a
single address and conduct up to four reads without reasserting
the address inputs. ADV/LD must be driven LOW to load a new
address into the SRAM, as described in the Single Read
Accesses section. The sequence of the burst counter is deter-
mined by the MODE input signal. A LOW input on MODE selects
a linear burst mode, a HIGH selects an interleaved burst
sequence. Both burst counters use A0 and A1 in the burst
sequence, and wraps around when incremented sufficiently. A
HIGH input on ADV/LD increments the internal burst counter
regardless of the state of chip enables inputs or WE. WE is
latched at the beginning of a burst cycle. Therefore, the type of
access (read or write) is maintained throughout the burst
sequence.
Single Write Accesses
Write accesses are initiated when the following conditions are
satisfied at clock rise: (1) CEN is asserted LOW, (2) CE1, CE2,
and CE3 are ALL asserted active, and (3) the signal WE is
asserted LOW. The address presented to the address inputs is
loaded into the Address Register. The write signals are latched
into the Control Logic block.
On the subsequent clock rise the data lines are automatically
tri-stated regardless of the state of the OE input signal. This
allows the external logic to present the data on DQ and DQP
(DQa,b,c,d/DQPa,b,c,d for CY7C1470BV25, DQa,b/DQPa,b for
CY7C1472BV25,
and
DQa,b,c,d,e,f,g,h/DQPa,b,c,d,e,f,g,h
for
CY7C1474BV25). In addition, the address for the subsequent
TMS
Test Mode Select
Synchronous
TMS Pin Controls the Test Access Port State Machine. Sampled on the rising edge of TCK.
TCK
JTAG Clock
Clock Input to the JTAG Circuitry.
VDD
Power Supply
Power Supply Inputs to the Core of the Device.
VDDQ
IO Power Supply Power Supply for the IO Circuitry.
VSS
Ground
Ground for the Device. Must be connected to ground of the system.
NC
–
No Connects. This pin is not connected to the die.
NC(144M,
288M,
576M, 1G)
–
These Pins are Not Connected. They are used for expansion to the 144M, 288M, 576M, and 1G
densities.
ZZ
Input-
Asynchronous
ZZ “Sleep” Input. This active HIGH input places the device in a non-time critical “sleep” condition
with data integrity preserved. For normal operation, this pin has must be LOW or left floating.
ZZ pin has an internal pull down.
Table 1. Pin Definitions (continued)
Pin Name
IO Type
Pin Description
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