notice. ISSI assumes no liability arising out of the application or use of any information, products or services described herein. Customers are advised to obtain the lat-
est version of this device specification before relying on any published information and before placing orders for products.
Integrated Silicon Solution, Inc. does not recommend the use of any of its products in life support applications where the failure or malfunction of the product can reason-
ably be expected to cause failure of the life support system or to significantly affect its safety or effectiveness. Products are not authorized for use in such applications
unless Integrated Silicon Solution, Inc. receives written assurance to its satisfaction, that:
a.) the risk of injury or damage has been minimized;
b.) the user assume all such risks; and
c.) potential liability of Integrated Silicon Solution, Inc is adequately protected under the circumstances
Integrated Silicon Solution, Inc.
- www.issi.com
Rev. A
07/18/2012
1
IS42S32800G, IS45S32800G
DEVICE OVERVIEW
The 256Mb SDRAM is a high speed CMOS, dynamic
random-access memory designed to operate in 3.3V V
dd
and 3.3V V
ddq
memory systems containing 268,435,456
bits. Internally configured as a quad-bank DRAM with a
synchronous interface. Each 67,108,864-bit bank is orga-
nized as 4,096 rows by 512 columns by 32 bits.
The 256Mb 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 256Mb 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 (FOR 2M
x
32
x
4
BANKS)
CLK
CKE
CS
RAS
CAS
WE
DQM0 - DQM3
COMMAND
DECODER
&
CLOCK
GENERATOR
DATA IN
BUFFER
32
32
4
MODE
REGISTER
12
REFRESH
CONTROLLER
DQ 0-31
SELF
REFRESH
CONTROLLER
A10
A11
A9
A8
A7
A6
A5
A4
A3
A2
A1
A0
BA0
BA1
12
32
DATA OUT
BUFFER
V
DD
/V
DDQ
V
ss
/V
ss
Q
32
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
9
512
(x 32)
BANK CONTROL LOGIC
BURST COUNTER
COLUMN
ADDRESS BUFFER
COLUMN DECODER
9
2
Integrated Silicon Solution, Inc.
- www.issi.com
Rev. A
07/18/2012
IS42S32800G, IS45S32800G
PIN CONFIGURATION
PACKAGE CODE: B 90 BALL TF-BGA (Top View) (8.00 mm x 13.00 mm Body, 0.8 mm Ball Pitch)
1 2 3 4 5 6 7 8 9
A
B
C
D
E
F
G
H
J
K
L
M
N
P
R
PIN DESCRIPTIONS
A0-A11
A0-A8
BA0, BA1
DQ0 to DQ31
CLK
CKE
CS
RAS
CAS
Row Address Input
Column Address Input
Bank Select Address
Data I/O
System Clock Input
Clock Enable
Chip Select
Row Address Strobe Command
Column Address Strobe Command
WE
DQM0-DQM3
V
dd
Vss
V
ddq
Vss
q
NC
Write Enable
x32 Input/Output Mask
Power
Ground
Power Supply for I/O Pin
Ground for I/O Pin
No Connection
DQ26 DQ24
VSS
VDD DQ23 DQ21
VDDQ VSSQ DQ19
DQ22 DQ20 VDDQ
DQ17 DQ18 VDDQ
NC
A2
A10
NC
BA0
CAS
VDD
DQ6
DQ1
DQ16 VSSQ
DQM2 VDD
A0
BA1
CS
A1
A11
RAS
DQ28 VDDQ VSSQ
VSSQ DQ27 DQ25
VSSQ DQ29 DQ30
VDDQ DQ31
VSS DQM3
A4
A7
CLK
DQM1
A5
A8
CKE
NC
NC
A3
A6
NC
A9
NC
VSS
WE
DQM0
DQ7 VSSQ
DQ5 VDDQ
DQ3 VDDQ
VDDQ DQ8
VSSQ DQ10 DQ9
VSSQ DQ12 DQ14
DQ11 VDDQ VSSQ
DQ13 DQ15
VSS
VDDQ VSSQ DQ4
VDD
DQ0
DQ2
3
Integrated Silicon Solution, Inc.
- www.issi.com
Rev. A
07/18/2012
IS42S32800G, IS45S32800G
PIN FUNCTIONS
Symbol
A0-A11
Type
Input Pin
Function (In Detail)
Address Inputs: A0-A11 are sampled during the ACTIVE
command (row-address A0-A11) and READ/WRITE command (column address
A0-A8), 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
determine 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.
DQM0 - DQM3 control the four bytes of the I/O buffers (DQ0-DQ31). In read
mode, DQMn control the output buffer. When DQMn is LOW, the corresponding buf-
fer byte is enabled, and when HIGH, disabled. The outputs go to the HIGH imped-
ance state whenDQMn is HIGH. This function corresponds to OE in conventional
DRAMs. In write mode, DQMn control the input buffer. When DQMn is LOW, the
corresponding buffer byte is enabled, and data can be written to the device. When
DQMn is HIGH, input data is masked and cannot be written to the device.
Data on the Data Bus is latched on these pins during Write commands, and buffered after
Read commands.
RAS,
in conjunction with
CAS
and
WE,
forms the device command. See the "Com-
mand Truth Table" item for details on device commands.
WE,
in conjunction with
RAS
and
CAS,
forms the device command. See the "Com-
mand Truth Table" item for details on device commands.
V
ddq
is the output buffer power supply.
V
dd
is the device internal power supply.
V
ssq
is the output buffer ground.
V
ss
is the device internal ground.
BA0, BA1
CAS
CKE
Input Pin
Input Pin
Input Pin
CLK
CS
Input Pin
Input Pin
D
QM0-DQM3
Input Pin
DQ0-DQ31
RAS
WE
V
ddq
V
dd
V
ssq
V
ss
I
nput/Output Pin
Input Pin
Input Pin
Power Supply Pin
Power Supply Pin
Power Supply Pin
Power Supply Pin
4
Integrated Silicon Solution, Inc.
- www.issi.com
Rev. A
07/18/2012
IS42S32800G, IS45S32800G
GENERAL DESCRIPTION
READ
The READ command selects the bank from BA0, BA1 inputs
and starts a burst read access to an active row. Inputs
A0-A8 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.
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.
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 for every T
ref
. 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-A8. 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.
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.
COMMAND INHIBIT
COMMAND INHIBIT prevents new commands from being
executed. Operations in progress are not affected, apart
from whether the CLK signal is enabled
NO OPERATION
When CS is low, the NOP command prevents unwanted
commands from being registered during idle or wait
states.
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
bank(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.
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
for accesses.
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 enable the AUTO
