liability arising out of the application or use of any information, products or services described herein. Customers are advised to obtain the latest version of this device specification before relying on
any published information and before placing orders for products.
Integrated Silicon Solution, Inc. — www.issi.com
Rev. D
01/13/2010
1
IS42S16400E
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
registered 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
A10
DQM
COMMAND
DECODER
&
CLOCK
GENERATOR
DATA IN
BUFFER
16
16
MODE
REGISTER
12
REFRESH
CONTROLLER
DQ 0-15
SELF
REFRESH
CONTROLLER
A11
A9
A8
A7
A6
A5
A4
A3
A2
A1
A0
BA0
BA1
12
16
DATA OUT
BUFFER
V
DD
/V
DDQ
GND/GNDQ
16
REFRESH
COUNTER
4096
4096
4096
4096
ROW DECODER
MULTIPLEXER
12
MEMORY CELL
ARRAY
ROW
ADDRESS
LATCH
12
ROW
ADDRESS
BUFFER
BANK 0
SENSE AMP I/O GATE
COLUMN
ADDRESS LATCH
8
256K
(x 16)
BANK CONTROL LOGIC
BURST COUNTER
COLUMN
ADDRESS BUFFER
COLUMN DECODER
8
2
www.issi.com — Integrated Silicon Solution, Inc.
Rev. D
01/13/2010
IS42S16400E
PIN FUNCTIONS
Symbol
A0-A11
TSOP Pin No.
23 to 26
29 to 34
22, 35
Type
Input Pin
Function (In Detail)
Address Inputs: A0-A11 are sampled during the ACTIVE
command (row-address A0-A11) and READ/WRITE command (A0-A7
with A10 defining auto precharge) to select one location out of the memory array
in the respective bank. A10 is sampled during a PRECHARGE command to deter-
mine if all banks are to be precharged (A10 HIGH) or bank selected by
BA0, BA1 (LOW). The address inputs also provide the op-code during a LOAD
MODE REGISTER command.
Bank Select Address: BA0 and BA1 defines which bank the ACTIVE, READ, WRITE
or PRECHARGE command is being applied.
CAS,
in conjunction with the
RAS
and
WE,
forms the device command. See the
"Command Truth Table" for details on device commands.
The CKE input determines whether the CLK input is enabled. The next rising edge
of the CLK signal will be valid when is CKE HIGH and invalid when LOW. When CKE
is LOW, the device will be in either power-down mode, clock suspend mode, or self
refresh mode. CKE is an asynchronous input.
CLK is the master clock input for this device. Except for CKE, all inputs to this device
are acquired in synchronization with the rising edge of this pin.
The CS input determines whether command input is enabled within the device.
Command input is enabled when
CS is LOW, and disabled with CS is HIGH. The
device remains in the previous state when
CS is HIGH.
DQ0 to DQ15 are I/O pins. I/O through these pins can be controlled in byte units
using the LDQM and UDQM pins.
BA0, BA1
CAS
CKE
20, 21
17
37
Input Pin
Input Pin
Input Pin
CLK
CS
38
19
Input Pin
Input Pin
DQ0 to
DQ15
LDQM,
UDQM
2, 4, 5, 7, 8, 10,
11,13, 42, 44, 45,
47, 48, 50, 51, 53
15, 39
DQ Pin
Input Pin
RAS
WE
V
DDq
V
DD
GND
q
GND
18
16
3, 9, 43, 49
1, 14, 27
6, 12, 46, 52
28, 41, 54
LDQM and UDQM control the lower and upper bytes of the I/O buffers. In read
mode, LDQM and UDQM control the output buffer. When LDQM or UDQM is LOW,
the corresponding buffer byte is enabled, and when HIGH, disabled. The outputs
go to the HIGH impedance state when LDQM/UDQM is HIGH. This function cor-
responds to
OE in conventional DRAMs. In write mode, LDQM and UDQM control
the input buffer. When LDQM or UDQM is LOW, the corresponding buffer byte is en-
abled, and data can be written to the device. When LDQM or UDQM is HIGH, input
data is masked and cannot be written to the device.
Input Pin
RAS,
in conjunction with
CAS
and
WE,
forms the device command. See the "Com-
mand Truth Table" item for details on device commands.
Input Pin
WE,
in conjunction with
RAS
and
CAS,
forms the device command. See the "Com-
mand Truth Table" item for details on device commands.
Power Supply Pin V
DDq
is the output buffer power supply.
Power Supply Pin V
DD
is the device internal power supply.
Power Supply Pin GND
q
is the output buffer ground.
Power Supply Pin GND is the device internal ground.
Integrated Silicon Solution, Inc. — www.issi.com
Rev. D
01/13/2010
3
IS42S16400E
READ
The READ command selects the bank from BA0, BA1 inputs
and starts a burst read access to an active row. Inputs
A0-A7 provides the starting column location. When A10 is
HIGH, this command functions as an AUTO PRECHARGE
command. When the auto precharge is selected, the row
being accessed will be precharged at the end of the READ
burst. The row will remain open for subsequent accesses
when AUTO PRECHARGE is not selected. DQ’s read
data is subject to the logic level on the DQM inputs two
clocks earlier. When a given DQM signal was registered
HIGH, the corresponding DQ’s will be High-Z two clocks
later. DQ’s will provide valid data when the DQM signal
was registered LOW.
AUTO PRECHARGE does not apply except in full-page
burst mode. Upon completion of the READ or WRITE
burst, a precharge of the bank/row that is addressed is
automatically performed.
AUTO REFRESH COMMAND
This command executes the AUTO REFRESH operation.
The row address and bank to be refreshed are automatically
generated during this operation. The stipulated period (t
rc
) is
required for a single refresh operation, and no other com-
mands can be executed during this period. This command is
executed at least 4096 times every 64ms. During an AUTO
REFRESH command, address bits are “Don’t Care”. This
command corresponds to CBR Auto-refresh.
WRITE
A burst write access to an active row is initiated with the
WRITE command. BA0, BA1 inputs selects the bank,
and the starting column location is provided by inputs
A0-A7. Whether or not AUTO-PRECHARGE is used is
determined by A10.
The row being accessed will be precharged at the end of
the WRITE burst, if AUTO PRECHARGE is selected. If
AUTO PRECHARGE is not selected, the row will remain
open for subsequent accesses.
A memory array is written with corresponding input data
on DQ’s and DQM input logic level appearing at the same
time. Data will be written to memory when DQM signal is
LOW. When DQM is HIGH, the corresponding data inputs
will be ignored, and a WRITE will not be executed to that
byte/column location.
SELF REFRESH
During the SELF REFRESH operation, the row address to
be refreshed, the bank, and the refresh interval are gen-
erated automatically internally. SELF REFRESH can be
used to retain data in the SDRAM without external clocking,
even if the rest of the system is powered down. The SELF
REFRESH operation is started by dropping the CKE pin
from HIGH to LOW. During the SELF REFRESH operation
all other inputs to the SDRAM become “Don’t Care”. The
device must remain in self refresh mode for a minimum
period equal to t
ras
or may remain in self refresh mode
for an indefinite period beyond that. The SELF-REFRESH
operation continues as long as the CKE pin remains LOW
and there is no need for external control of any other pins.
The next command cannot be executed until the device
internal recovery period (t
rc
) has elapsed. Once CKE
goes HIGH, the NOP command must be issued (minimum
of two clocks) to provide time for the completion of any
internal refresh in progress. After the self-refresh, since it
is impossible to determine the address of the last row to
be refreshed, an AUTO-REFRESH should immediately be
performed for all addresses.
PRECHARGE
The PRECHARGE command is used to deactivate the
open row in a particular bank or the open row in all banks.
BA0, BA1 can be used to select which bank is precharged
or they are treated as “Don’t Care”. A10 determined
whether one or all banks are precharged. After execut-
ing this command, the next command for the selected
banks(s) is executed after passage of the period t
RP
, which
is the period required for bank precharging. Once a bank
has been precharged, it is in the idle state and must be
activated prior to any READ or WRITE commands being
issued to that bank.
BURST TERMINATE
The BURST TERMINATE command forcibly terminates
the burst read and write operations by truncating either
fixed-length or full-page bursts and the most recently
registered READ or WRITE command prior to the BURST
TERMINATE.
AUTO PRECHARGE
The AUTO PRECHARGE function ensures that the pre-
charge is initiated at the earliest valid stage within a burst.
This function allows for individual-bank precharge without
requiring an explicit command. A10 to enables the AUTO
PRECHARGE function in conjunction with a specific READ
or WRITE command. For each individual READ or WRITE
command, auto precharge is either enabled or disabled.
4
COMMAND INHIBIT
COMMAND INHIBIT prevents new commands from being
executed. Operations in progress are not affected, apart
from whether the CLK signal is enabled
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Rev. D
01/13/2010
IS42S16400E
NO OPERATION
When
CS is low, the NOP command prevents unwanted
commands from being registered during idle or wait
states.
LOAD MODE REGISTER
During the LOAD MODE REGISTER command the mode
register is loaded from A0-A11. This command can only
be issued when all banks are idle.
ACTIVE COMMAND
When the ACTIVE COMMAND is activated, BA0, BA1
inputs selects a bank to be accessed, and the address
inputs on A0-A11 selects the row. Until a PRECHARGE
command is issued to the bank, the row remains open
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