mt18vddt12872ag-40b Micron Semiconductor Products, mt18vddt12872ag-40b Datasheet - Page 7

• Manufacturer Part Number: mt18vddt12872ag-40b
• Description: 256mb, 512mb, 1gb, 2gb X72, Ecc, Dr 184-pin Ddr Sdram Udimm
• Manufacturer: Micron Semiconductor Products

General Description
Serial Presence-Detect Operation
PDF: 09005aef80814e61/Source: 09005aef807f8acb
DD18C32_64_128_256x72A.fm - Rev. C 10/07 EN
The MT18VDDT3272A, MT18VDDT6472A, MT18VDDT12872A, and MT18VDDT25672A
are high-speed CMOS, dynamic random access 256MB, 512MB, 1GB, and 2GB memory
modules 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 corre-
sponding 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.
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
the master (system logic) and the slave EEPROM device (DIMM) occur via a standard I
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 V
module, permanently disabling hardware write protect.
256MB, 512MB, 1GB, 2GB (x72, ECC, DR) 184-Pin DDR SDRAM UDIMM
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Micron Technology, Inc., reserves the right to change products or specifications without notice.
©2004 Micron Technology, Inc. All rights reserved.
General Description
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