mt18vddf12872dg-335 Micron Semiconductor Products, mt18vddf12872dg-335 Datasheet - Page 8

• Manufacturer Part Number: mt18vddf12872dg-335
• Description: 512mb, 1gb X72, Ecc, Dr 184-pin Ddr Sdram Rdimm
• Manufacturer: Micron Semiconductor Products

General Description
Register and PLL Operation
Serial Presence-Detect Operation
PDF: 09005aef807eb17d/Source: 09005aef807d24c9
DDF18C64_128x72D.fm - Rev. C 1/08 EN
The MT18VDDF6472D and MT18VDDF12872D are high-speed, CMOS dynamic random
access 512MB and 1GB 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.
Control, command, and address 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.
These DDR SDRAM modules operate in registered mode, where the control, command,
and address input signals are latched in the registers on the rising clock edge and sent to
the DDR SDRAM devices on the following rising clock edge (data access is delayed by
one clock cycle). A phase-lock loop (PLL) on the module receives and redrives the differ-
ential clock signals (CK, CK#) to the DDR SDRAM devices. The register(s) and PLL reduce
clock, control, command, and address signal loading by isolating DRAM from the system
controller. PLL clock timing is defined by JEDEC specifications and ensured by use of the
JEDEC clock reference board. Registered mode will add one clock cycle to CL.
DDR SDRAM modules incorporate serial presence-detect. The SPD function is imple-
mented 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
DRAM 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
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.
512MB, 1GB (x72, ECC, DR) 184-Pin DDR SDRAM RDIMM
8
Micron Technology, Inc., reserves the right to change products or specifications without notice.
General Description
©2004 Micron Technology, Inc. All rights reserved
SS
on the
2
C bus using