1GB (x72, ECC, DR) 200-Pin DDR SDRAM SODIMM
General Description
General Description
The MT18VDDF12872H is a high-speed, CMOS, dynamic random access, 1GB memory
module organized in a x72 configuration. These modules use DDR SDRAM devices with
four internal banks.
DDR SDRAM modules use a double data rate architecture to achieve high-speed opera-
tion. 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 DDR SDRAM modules effectively consists of a single 2n-bit wide,
one-clock-cycle data transfer at the internal DRAM core and two corresponding n-bit
wide, one-half-clock-cycle data transfers 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 a 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 differential clock inputs (CK and CK#); the crossing
of CK going HIGH and CK# going LOW will be referred to as the positive edge of CK.
Commands 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.
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 are programmed 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
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the master (system logic) and the slave EEPROM device (DIMM) occur via a standard I C
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 VSS on the
module, permanently disabling hardware write protect.
PDF: 09005aef80e4880c/Source: 09005aef80e487d7
DDF18C128x72H.fm - Rev. B 10/07 EN
Micron Technology, Inc., reserves the right to change products or specifications without notice.
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©2004 Micron Technology, Inc. All rights reserved.
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