128K x 36, 256K x 18
3.3V Synchronous ZBT™ SRAMs
2.5V I/O, Burst Counter
Pipelined Outputs
x
x
IDT71V2556S
IDT71V2558S
IDT71V2556SA
IDT71V2558SA
Features
128K x 36, 256K x 18 memory configurations
Supports high performance system speed - 200 MHz
(3.2 ns Clock-to-Data Access)
ZBT
TM
Feature - No dead cycles between write and read
cycles
Internally synchronized output buffer enable eliminates the
need to control
OE
Single R/W (READ/WRITE) control pin
W
Positive clock-edge triggered address, data, and control
signal registers for fully pipelined applications
4-word burst capability (interleaved or linear)
BW
Individual byte write (BW
1
-
BW
4
) control (May tie active)
Three chip enables for simple depth expansion
3.3V power supply (±5%), 2.5V I/O Supply (V
DDQ)
Optional - Boundary Scan JTAG Interface (IEEE 1149.1
complaint)
Packaged in a JEDEC standard 100-pin plastic thin quad
flatpack (TQFP), 119 ball grid array (BGA) and 165 fine pitch
ball grid array (fBGA)
x
x
x
x
x
x
x
x
x
x
Description
The IDT71V2556/58 are 3.3V high-speed 4,718,592-bit (4.5 Mega-
bit) synchronous SRAMS. They are designed to eliminate dead bus cycles
when turning the bus around between reads and writes, or writes and
reads. Thus, they have been given the name ZBT
TM
, or Zero Bus
Turnaround.
Address and control signals are applied to the SRAM during one clock
cycle, and two cycles later the associated data cycle occurs, be it read
or write.
The IDT71V2556/58 contain data I/O, address and control signal
registers. Output enable is the only asynchronous signal and can be used
to disable the outputs at any given time.
A Clock Enable (CEN) pin allows operation of the IDT71V2556/58 to
be suspended as long as necessary. All synchronous inputs are ignored
when (CEN) is high and the internal device registers will hold their previous
values.
There are three chip enable pins (CE
1
, CE
2
,
CE
2
) that allow the user
to deselect the device when desired. If any one of these three are not
asserted when ADV/LD is low, no new memory operation can be initiated.
However, any pending data transfers (reads or writes) will be completed.
The data bus will tri-state two cycles after chip is deselected or a write is
initiated.
The IDT71V2556/58 has an on-chip burst counter. In the burst mode,
the IDT71V2556/58 can provide four cycles of data for a single address
presented to the SRAM. The order of the burst sequence is defined by the
LBO
input pin. The
LBO
pin selects between linear and interleaved burst
sequence. The ADV/LD signal is used to load a new external address
(ADV/LD = LOW) or increment the internal burst counter (ADV/LD =
HIGH).
The IDT71V2556/58 SRAMs utilize IDT's latest high-performance
CMOS process and are packaged in a JEDEC standard 14mm x 20mm
100-pin thin plastic quad flatpack (TQFP) as well as a 119 ball grid array
(BGA) and a 165 fine pitch ball grid array (fBGA).
Pin Description Summary
A
0
-A
17
Address Inputs
Chip Enables
Output Enable
Read/Write Signal
Clock Enable
Individual Byte Write Selects
Clock
Advance burst address / Load new address
Linear / Interleaved Burst Order
Test Mode Select
Test Data Input
Test Clock
Test Data Output
JTAG Reset (Optional)
Sleep Mode
Data Input / Output
Core Power, I/O Power
Ground
Input
Input
Input
Input
Input
Input
Input
Input
Input
Input
Input
Input
Output
Input
Input
I/O
Supply
Supply
Synchronous
Synchronous
Asynchronous
Synchronous
Synchronous
Synchronous
N/A
Synchronous
Static
Synchronous
Synchronous
N/A
Synchronous
Asynchronous
Synchronous
Synchronous
Static
Static
CE
1
, CE
2
,
CE
2
OE
R/
W
CEN
BW
1
,
BW
2
,
BW
3
,
BW
4
CLK
ADV/
LD
LBO
TMS
TDI
TCK
TDO
TRST
ZZ
I/O
0
-I/O
31
, I/O
P1
-I/O
P4
V
DD
, V
DDQ
V
SS
1
©2004 Integrated Device Technology, Inc.
OCTOBER 2004
DSC-4875/08
4875 tbl 01
IDT [ INTEGRATED DEVICE TECHNOLOGY ]
