Internet Data Sheet
HYB25D128xxxC[C/E/F/T](L)
128-Mbit Double-Data-Rate SDRAM
1.2
Description
Read and write accesses to the DDR SDRAM 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 followed by a Read or Write
command. The address bits registered coincident with the
Active command are used to select the bank and row to be
accessed. The address bits registered coincident with the
Read or Write command are used to select the bank and the
starting column location for the burst access.
The DDR SDRAM 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 SDRAMs, the pipelined, multibank
architecture of
DDR SDRAMs allows for concurrent
operation, thereby providing 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 compatible with the JEDEC
Standard for SSTL_2. All outputs are SSTL_2, Class II
compatible.
Note: The functionality described and the timing
specifications included in this data sheet are for the
DLL Enabled mode of operation.
The 128-Mbit Double-Data-Rate SDRAM is a high-speed
CMOS, dynamic random-access memory containing
134,217,728 bits. It is internally configured as a quad-bank
DRAM.
The 128-Mbit Double-Data-Rate SDRAM uses a double-
data-rate architecture 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
128-Mbit Double-Data-Rate SDRAM
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.
The 128-Mbit Double-Data-Rate SDRAM operates from a
differential clock (CK and CK; the crossing of CK going HIGH
and CK going LOW is 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.
Rev. 1.6, 2007-02
03292006-U5AN-6TI1
4
QIMONDA [ QIMONDA AG ]
