The GS88237AB is a 9,437,184-bit high performance
synchronous SRAM with a 2-bit burst address counter. Although
of a type originally developed for Level 2 Cache applications
supporting high performance CPUs, the device now finds
application in synchronous SRAM applications, ranging from
DSP main store to networking chip set support.
Controls
Addresses, data I/Os, chip enable (E1), address burst control
inputs (ADSP
) are synchronous and are controlled by a positive-edge-
GW
triggered clock input (CK). Output enable (G
control (ZZ) are asynchronous inputs. Burst cycles can be initiated
with either ADSP
burst addresses are generated internally and are controlled by
. The burst address counter may be configured to count in
ADV
either linear or interleave order with the Linear Burst Order (LBO
input. The Burst function need not be used. New addresses can be
loaded on every cycle with no degradation of chip performance.
, ADSC, ADV), and write control inputs (Bx, BW,
) and power down
or ADSC inputs. In Burst mode, subsequent
250 MHz–133 MHz
2.5 V or 3.3 V V
2.5 V or 3.3 V I/O
SCD and DCD Pipelined Reads
The GS88237AB is a SCD (Single Cycle Deselect) and DCD
(Dual Cycle Deselect) pipelined synchronous SRAM.
SRAMs pipeline disable commands to the same degree as read
commands. SCD SRAMs pipeline deselect commands one stage
less than read commands. SCD RAMs begin turning off their
outputs immediately after the deselect command has been
captured in the input registers. DCD RAMs hold the deselect
command for one full cycle and then begin turning off their
outputs just after the second rising edge of clock. The user may
configure this SRAM for either mode of operation using the SCD
mode input.
Byte Write and Global Write
Byte write operation is performed by using Byte Write enable
) input combined with one or more individual byte write
(BW
signals (Bx
writing all bytes at one time, regardless of the Byte Write control
inputs.
FLXDrive™
The ZQ pin allows selection between high drive strength (ZQ low)
for multi-drop bus applications and normal drive strength (ZQ
floating or high) point-to-point applications. See the Output Driver
Characteristics chart for details.
Sleep Mode
Low power (Sleep mode) is attained through the assertion (High)
of the ZZ signal, or by stopping the clock (CK). Memory data is
retained during Sleep mode.
Core and Interface Voltages
The GS88237AB operates on a 2.5 V or 3.3 V power supply. All
input are 3.3 V and 2.5 V compatible. Separate output power
)
(V
DDQ
circuits and are 3.3 V and 2.5 V compatible.
). In addition, Global Write (GW) is available for
) pins are used to decouple output noise from the internal
Specifications cited are subject to change without notice. For latest documentation see http://www.gsitechnology.com.
Mode Pin Functions
GS88237AB-250/225/200/166/150/133
Mode Name
Burst Order ControlLBO
Power Down ControlZZ
Note:
There is a pull-down device on the ZZ pin, so this input pin can be unconnected and the chip will operate in the default states as specified in the
above tables.
Burst Counter Sequences
A[1:0] A[1:0] A[1:0] A[1:0]
1st address00011011
2nd address01101100
3rd address10110001
4th address11000110
Note:
The burst counter wraps to initial state on the 5th clock.
Pin
Name
StateFunction
LLinear Burst
HInterleaved Burst
L or NCActive
H
Standby, I
Note:
The burst counter wraps to initial state on the 5th clock.
Specifications cited are subject to change without notice. For latest documentation see http://www.gsitechnology.com.
GS88237AB-250/225/200/166/150/133
Synchronous Truth Table
State
OperationAddress Used
Deselect Cycle, Power DownNoneXHXLXXHigh-Z
Read Cycle, Begin BurstExternalRLLXXXQ
Read Cycle, Begin BurstExternalRLHLXFQ
Write Cycle, Begin BurstExternalWLHLXTD
Read Cycle, Continue BurstNextCRXHHLFQ
Read Cycle, Continue BurstNextCRHXHLFQ
Write Cycle, Continue BurstNextCWXHHLTD
Write Cycle, Continue BurstNextCWHXHLTD
Read Cycle, Suspend BurstCurrentXHHHFQ
Read Cycle, Suspend BurstCurrentHXHHFQ
Diagram
5
Key
E1ADSPADSCADV
W
3
DQ
4
Write Cycle, Suspend BurstCurrentXHHHTD
Write Cycle, Suspend BurstCurrentHXHHTD
Notes:
1.X = Don’t Care, H = High, L = Low
2.W = T (True) and F (False) is defined in the Byte Write Truth Table preceding
3.G
is an asynchronous input. G can be driven high at any time to disable active output drivers. G low can only enable active drivers (shown
as “Q” in the Truth Table above).
4.All input combinations shown above are tested and supported. Input combinations shown in gray boxes need not be used to accomplish
basic synchronous or synchronous burst operations and may be avoided for simplicity.
5.Tying ADSP
6.Tying ADSP
high and ADSC low allows simple non-burst synchronous operations. See BOLD items above.
high and ADV low while using ADSC to load new addresses allows simple burst operations. See ITALIC items above.