IS42S16400A
ISSI
®
GENERAL DESCRIPTION
The 64Mb SDRAM is a high speed CMOS, dynamic
random-access memory designed to operate in 3.3V
memory systems containing 67,108,864 bits. Internally
configured as a quad-bank DRAM with a synchronous
interface. Each 16,777,216-bit bank is organized as 4,096
rows by 256 columns by 16 bits.
The 64Mb SDRAM includes an AUTO REFRESH MODE,
and a power-saving, power-down mode. All signals are
registered on the positive edge of the clock signal, CLK.
All inputs and outputs are LVTTL compatible.
The 64Mb SDRAM has the ability to synchronously burst
data at a high data rate with automatic column-address
generation, the ability to interleave between internal banks
to hide precharge time and the capability to randomly
change column addresses on each clock cycle during
burst access.
A self-timed row precharge initiated at the end of the burst
sequence is available with the AUTO PRECHARGE
function enabled. Precharge one bank while accessing one
of the other three banks will hide the precharge cycles and
provide seamless, high-speed, random-access operation.
SDRAM read and write accesses are burst oriented starting
at a selected location and continuing for a programmed
number of locations in a programmed sequence. The
registration of an ACTIVE command begins accesses,
followed by a READ or WRITE command. The ACTIVE
command in conjunction with address bits registered are
used to select the bank and row to be accessed (BA0, BA1
select the bank; A0-A11 select the row). The READ or
WRITE commands in conjunction with address bits reg-
istered are used to select the starting column location for
the burst access.
Programmable READ or WRITE burst lengths consist of
1, 2, 4 and 8 locations or full page, with a burst terminate
option.
FUNCTIONAL BLOCK DIAGRAM
CLK
CKE
CS
RAS
CAS
WE
A11
DQM
COMMAND
DECODER
&
CLOCK
GENERATOR
DATA IN
BUFFER
16
16
MODE
REGISTER
11
REFRESH
CONTROLLER
I/O 0-15
SELF
REFRESH
CONTROLLER
A10
A9
A8
A7
A6
A5
A4
A3
A2
A1
A0
BA0
BA1
11
DATA OUT
BUFFER
16
16
Vcc/Vcc
Q
GND/GNDQ
REFRESH
COUNTER
4096
4096
4096
4096
ROW DECODER
MULTIPLEXER
MEMORY CELL
ARRAY
11
ROW
ADDRESS
LATCH
11
ROW
ADDRESS
BUFFER
BANK 0
SENSE AMP I/O GATE
COLUMN
ADDRESS LATCH
8
256K
(x 16)
BANK CONTROL LOGIC
BURST COUNTER
COLUMN DECODER
COLUMN
ADDRESS BUFFER
8
2
Integrated Silicon Solution, Inc. — www.issi.com —
1-800-379-4774
Rev.C
04/16/03
ISSI [ INTEGRATED SILICON SOLUTION, INC ]
