WED2ZL361MS42BI Ver la hoja de datos (PDF) - White Electronic Designs Corporation
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WED2ZL361MS42BI Datasheet PDF : 12 Pages
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White Electronic Designs
WED2ZL361MS
FUNCTION DESCRIPTION
The WED2ZL361MS is an NBL SSRAM designed to sus-
tain 100% bus bandwidth by eliminating turnaround cycle
when there is transition from Read to Write, or vice versa.
All inputs (with the exception of OE#, LBO# and ZZ) are
synchronized to rising clock edges.
All read, write and deselect cycles are initiated by the
ADV# input. Subsequent burst addresses can be internally
generated by the burst advance pin (ADV#). ADV# should
be driven to Low once the device has been deselected in
order to load a new address for next operation.
Clock Enable (CKE#) pin allows the operation of the chip to
be suspended as long as necessary. When CKE# is high,
all synchronous inputs are ignored and the internal device
registers will hold their previous values. NBL SSRAM
latches external address and initiates a cycle when CKE#
and ADV# are driven low at the rising edge of the clock.
Output Enable (OE#) can be used to disable the output
at any given time. Read operation is initiated when at the
rising edge of the clock, the address presented to the ad-
dress inputs are latched in the address register, CKE# is
driven low, the write enable input signals WE# are driven
high, and ADV# driven low. The internal array is read
between the first rising edge and the second rising edge
of the clock and the data is latched in the output register.
At the second clock edge the data is driven out of the
SRAM. During read operation OE# must be driven low for
the device to drive out the requested data.
Write operation occurs when WE# is driven low at the ris-
ing edge of the clock. BW#[d:a] can be used for byte write
operation. The pipe-lined NBL SSRAM uses a late-late write
cycle to utilize 100% of the bandwidth. At the first rising edge
of the clock, WE# and address are registered, and the data
associated with that address is required two cycle later.
Subsequent addresses are generated by ADV# High for
the burst access as shown below. The starting point of the
burst seguence is provided by the external address. The
burst address counter wraps around to its initial state upon
completion. The burst sequence is determined by the state
of the LBO# pin. When this pin is low, linear burst sequence
is selected. And when this pin is high, Interleaved burst
sequence is selected.
During normal operation, ZZ must be driven low. When ZZ
is driven high, the SRAM will enter a Power Sleep Mode
after 2 cycles. At this time, internal state of the SRAM is
preserved. When ZZ returns to low, the SRAM operates
after 2 cycles of wake up time.
BURST SEQUENCE TABLE
(INTERLEAVED BURST, LBO# = HIGH)
(LINEAR BURST, LBO# = LOW)
LBO# Pin High
First Address
↓
Fourth Address
Case 1
A1 A0
00
01
10
11
Case 2
A1 A0
01
00
11
10
Case 3
A1 A0
10
11
00
01
Case 4
A1 A0
11
10
01
00
NOTE 1: LBO# pin must be tied to High or Low, and Floating State must not be
allowed.
LBO# Pin High
First Address
↓
Fourth Address
Case 1
A1 A0
00
01
10
11
Case 2
A1 A0
01
10
11
00
Case 3
A1 A0
10
11
00
01
Case 4
A1 A0
11
00
01
10
White Electronic Designs Corp. reserves the right to change products or specifications without notice.
Oct, 2002
Rev. 5
2
White Electronic Designs Corporation • (602) 437-1520 • www.wedc.com
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