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. 00C
11/20/07
1
IS42VS16400E
GENERAL DESCRIPTION
The 64Mb SDRAM is a high speed CMOS, dynamic
random-access memory designed to operate in 1.8V 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 and deep 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 func-
tion 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 num-
ber of locations in a programmed sequence. The registra-
tion 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
DATA OUT
BUFFER
16
16
V
DD
/V
DDQ
GND/GNDQ
REFRESH
COUNTER
4096
4096
4096
4096
ROW DECODER
MULTIPLEXER
MEMORY CELL
ARRAY
12
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 DECODER
COLUMN
ADDRESS BUFFER
8
2
Integrated Silicon Solution, Inc. — www.issi.com
Rev. 00C
11/20/07
IS42VS16400E
PIN FUNCTIONS
Symbol
A0-A11
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 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.
Input Pin
Bank Select Address: BA0 and BA1 defines which bank the ACTIVE, READ, WRITE or
PRECHARGE command is being applied. These pins also select between the mode
register and the extended mode register.
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.
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 corresponds 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 enabled, 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.
RAS,
in conjunction with
CAS
and
WE,
forms the device command. See the "Command
Truth Table" item for details on device commands.
WE,
in conjunction with
RAS
and
CAS,
forms the device command. See the "Command
Truth Table" item for details on device commands.
V
DDQ
is the output buffer power supply.
V
DD
is the device internal power supply.
GND
Q
is the output buffer ground.
GND is the device internal ground.
BA0, BA1
20, 21
CAS
CKE
17
37
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
Input Pin
Input Pin
Power Supply Pin
Power Supply Pin
Power Supply Pin
Power Supply Pin
Integrated Silicon Solution, Inc. — www.issi.com
Rev. 00C
11/20/07
3
IS42VS16400E
FUNCTION
(In Detail)
A0-A11 are address inputs sampled during the ACTIVE
(row-address A0-A11) and READ/WRITE command (A0-A7 with
A10 defining auto PRECHARGE). 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 en-
abled. 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 synchroniza-
tion with the rising edge of this pin.
The
CS
input determines whether command input is en-
abled 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 DQ
pins. DQ through these pins can be controlled in byte units
using the LDQM and UDQM pins.
LDQM and UDQM control the lower and upper bytes of the
DQ buffers. In read mode, LDQM and UDQM control the
output buffer. When LDQM or UDQM is LOW, the corre-
sponding buffer byte is enabled, and when HIGH, disabled.
The outputs go to the HIGH Impedance State when LDQM/
UDQM is HIGH. This function corresponds to
OE
in conven-
tional DRAMs. In write mode, LDQM and UDQM control the
input buffer. When LDQM or UDQM is LOW, the correspond-
ing buffer byte is enabled, 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.
RAS,
in conjunction with
CAS
and
WE
, forms the device
command. See the “Command Truth Table” item for details
on device commands.
WE
, in conjunction with
RAS
and
CAS
, forms the device
command. See the “Command Truth Table” item for details
on device commands.
V
DDQ
is the output buffer power supply.
V
DD
is the device internal power supply.
GND
Q
is the output buffer ground.
GND is the device internal ground.
4
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.
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.
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 executing 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.
AUTO PRECHARGE
The AUTO PRECHARGE function ensures that the precharge
is initiated at the earliest valid stage within a burst. This
function allows for individual-bank precharge without requir-
ing 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.
AUTO PRECHARGE does not apply except in full-page
Integrated Silicon Solution, Inc. — www.issi.com
Rev. 00C
11/20/07
IS42VS16400E
burst mode. Upon completion of the READ or WRITE burst,
a precharge of the bank/row that is addressed is automati-
cally performed.
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 TERMI-
NATE.
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.
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.
SELF REFRESH
During the SELF REFRESH operation, the row address to
be refreshed, the bank, and the refresh interval are gener-
ated 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 impos-
sible to determine the address of the last row to be
refreshed, an AUTO-REFRESH should immediately be
performed for all addresses.
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.
DEEP POWER DOWN
The operating mode, deep power-down achieves maximum
power reduction by eliminating the power of the whole
memory array of the device. Array data will not be retained
once the device enters deep power-down mode.
This mode is entered by having all banks idle with
CS
and
WE
held LOW;
RAS
and
CAS
held HIGH at the rising edge
of the clock, while CKE is LOW. This mode is exited by
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