GS841E18AT Datasheet, PDF (1/21 Pages) GSI Technology – 256K x 18 Sync Cache Tag

GS841E18AT/B-180/166/150/130/100
TQFP, BGA
Commercial Temp
Industrial Temp
256K x 18 Sync
Cache Tag
180 MHz–100 MHz
3.3 V V_DD
3.3 V and 2.5 V I/O
Features
• 3.3 V +10%/–5% core power supply, 2.5 V or 3.3 V I/O
supply
• Dual Cycle Deselect (DCD)
• Intergrated data comparator for Tag RAM application
• FT mode pin for flow through or pipeline operation
• LBO pin for Linear or Interleave (Pentium^TM and X86) Burst
mode
• Synchronous address, data I/O, and control inputs
• Synchronous Data Enable (DE)
• Asynchronous Output Enable (OE)
• Asynchronous Match Output Enable (MOE)
• Byte Write (BWE) and Global Write (GW) operation
• Three chip enable signals for easy depth expansion
• Internal self-timed write cycle
• JTAG Test mode conforms to IEEE standard 1149.1
• JEDEC-standard 100-lead TQFP package and 119-BGA
• Pb-Free 100-lead TQFP package available
Functional Description
The GS841E18A is a 256K x 18 high performance synchronous DCD
SRAM with integrated Tag RAM comparator. A 2-bit burst counter is
included to provide burst interface with Pentium^TM and other high
performance CPUs. It is designed to be used as a Cache Tag SRAM,
as well as data SRAM. Addresses, data IOs, match output, chip
enables (CE1, CE2, CE3), address control inputs (ADSP, ADSC,
ADV), and write control inputs (BW1, BW2, BWE, GW, DE) are
synchronous and are controlled by a positive-edge-triggered clock
(CLK).
Output Enable (OE), Match Output Enable, and power down control
(ZZ) are asynchronous. Burst can be initiated with either ADSP or
ADSC inputs. Subsequent burst addresses are generated internally and
are controlled by ADV. The burst sequence is either interleave order
(Pentium^TM or x86) or linear order, and is controlled by LBO.
Output registers and the Match output register are provided and
controlled by the FT mode pin (Pin 14). Through use of the FT mode
pin, I/O registers can be programmed to perform pipeline or flow
through operation. Flow Through mode reduces latency.
Byte write operation is performed by using Byte Write Enable (BWE)
input combined with two individual byte write signals BW1-2. In
addition, Global Write (GW) is available for writing all bytes at one
time.
Compare cycles begin as a read cycle with output disabled so that
compare data can be loaded into the data input register. The
comparator compares the read data with the registered input data and a
match signal is generated. The match output can be either in Pipeline
or Flow Through modes controlled by the FT signal.
Low power (Standby mode) is attained through the assertion of the ZZ
signal, or by stopping the clock (CLK). Memory data is retained
during Standby mode.
JTAG boundary scan interface is provided using IEEE standard
1149.1 protocol. Four pins—Test Data In (TDI), Test Data Out
(TDO), Test Clock (TCK) and Test Mode Select (TMS)—are used to
perform JTAG function.
The GS841E18A operates on a 3.3 V power supply and all inputs/
outputs are 3.3 V- or 2.5 V-LVTTL-compatible. Separate output
(V_DDQ) pins are used to allow both 3.3 V or 2.5 V IO interface.
Dual Cycle Deselect (DCD)
The GS841E18A is a DCD pipelines synchronous SRAM. DCD
SRAMs pipeline disable commands to the same degree as read
commands. DCD SRAMs hold the deselect command for one full
cycle and then begin turning off their outputs just after the second
rising edge of the clock.
Pipeline
3-1-1-1
Flow
Through
2-1-1-1
Parameter Synopsis
–180 -166 -150 -133 -100
t_{cycle 5.5 ns 6.0 ns 6.6 ns 7.5 ns 10 ns}
t_KQ 3.2 ns 3.5 ns 3.8 ns 4.0 ns 4.5 ns
I_DD 335 mA 310 mA 275 mA 250 mA 190 mA
t_KQ
8 ns 8.5 ns 10 ns 11 ns 12 ns
t_cycle 9.1 ns 10 ns 10 ns 15 ns 15 ns
I_DD 210 mA 190 mA 190 mA 140 mA 140 mA
Rev: 1.03 4/2005
1/21
© 2001, GSI Technology
Specifications cited are subject to change without notice. For latest documentation see http://www.gsitechnology.com. * Pentium is a trademark of Intel