512MB, 1GB (x64)
200-PIN DDR SODIMM
General Description
The MT16VDDF6464H and MT16VDDF12864H are
high-speed CMOS, dynamic random-access, 512MB
and 1GB memory modules organized in a x64 configu-
ration. These modules use internally configured quad-
bank DRAM devices.
high effective bandwidth by hiding row precharge and
activation time.
An auto refresh mode is provided, along with a
power-saving power-down mode. All inputs are com-
patible with the JEDEC Standard for SSTL_2. All out-
puts are SSTL_2, Class II compatible. For more
information regarding DDR SDRAM operation, refer to
the 256Mb or 512Mb DDR SDRAM data sheets.
DDR SDRAM modules use a double data rate archi-
tecture to achieve high-speed operation. The double
data rate architecture is essentially a 2n-prefetch
architecture with an interface designed to transfer two
data words per clock cycle at the I/O pins. A single read
or write access for the DDR SDRAM module effectively
consists of a single 2n-bit wide, one-clock-cycle data
transfer at the internal DRAM core and two corre-
sponding n-bit wide, one-half-clock-cycle data trans-
fers at the I/O pins.
A bidirectional data strobe (DQS) is transmitted
externally, along with data, for use in data capture at
the receiver. DQS is an intermittent strobe transmitted
by the DDR SDRAM during READs and by the memory
controller during WRITEs. DQS is edge-aligned with
data for READs and center-aligned with data for
WRITEs.
DDR SDRAM modules operate from a differential
clock (CK and CK#); the crossing of CK going HIGH
and CK# going LOW will be referred to as the positive
edge of CK. Commands (address and control signals)
are registered at every positive edge of CK. Input data
is registered on both edges of DQS, and output data is
referenced to both edges of DQS, as well as to both
edges of CK.
Read and write accesses to DDR SDRAM modules
are burst oriented; accesses start at a selected location
and continue for a programmed number of locations
in a programmed sequence. Accesses begin with the
registration of an ACTIVE command, which is then fol-
lowed by a READ or WRITE command. The address
bits registered coincident with the ACTIVE command
are used to select the device bank and row to be
accessed (BA0, BA1 select devices bank; A0–A12 select
device row). The address bits registered coincident
with the READ or WRITE command are used to select
the device bank and the starting device column loca-
tion for the burst access.
Serial Presence-Detect Operation
DDR SDRAM modules incorporate serial presence-
detect (SPD). The SPD function is implemented using
a 2,048-bit EEPROM. This nonvolatile storage device
contains 256 bytes. The first 128 bytes can be pro-
grammed by Micron to identify the module type and
various SDRAM organizations and timing parameters.
The remaining 128 bytes of storage are available for
use by the customer. System READ/WRITE operations
between the master (system logic) and the slave
EEPROM device (DIMM) occur via a standard I2C bus
using the DIMM’s SCL (clock) and SDA (data) signals,
together with SA (2:0), which provide eight unique
DIMM/EEPROM addresses. Write protect (WP) is tied
to ground on the module, permanently disabling hard-
ware write protect.
Mode Register Definition
The mode register is used to define the specific
mode of operation of the DDR SDRAM. This definition
includes the selection of a burst length, a burst type, a
CAS latency and an operating mode, as shown in
Figure 5, Mode Register Definition Diagram, on page 9.
The mode register is programmed via the MODE REG-
ISTER SET command (with BA0 = 0 and BA1 = 0) and
will retain the stored information until it is pro-
grammed again or the device loses power (except for
bit A8, which is self-clearing).
Reprogramming the mode register will not alter the
contents of the memory, provided it is performed cor-
rectly. The mode register must be loaded (reloaded)
when all device banks are idle and no bursts are in
progress, and the controller must wait the specified
time before initiating the subsequent operation. Vio-
lating either of these requirements will result in
unspecified operation.
Mode register bits A0–A2 specify the burst length,
A3 specifies the type of burst (sequential or inter-
leaved), A4–A6 specify the CAS latency, and A7–A12
specify the operating mode.
DDR SDRAM modules provides for programmable
read or write burst lengths of 2, 4, or 8 locations. An
auto precharge function may be enabled to provide a
self-timed row precharge that is initiated at the end of
the burst access.
As with standard SDR SDRAM modules, the pipe-
lined, multibank architecture of DDR SDRAM modules
allows for concurrent operation, thereby providing
09005aef80a646bc
DDF16C64_128x64HG_B.fm - Rev. B 7/03 EN
Micron Technology, Inc., reserves the right to change products or specifications without notice.
©2003 Micron Technology, Inc.
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