hyb18t512161bf-33 Infineon Technologies Corporation, hyb18t512161bf-33 Datasheet - Page 20

• Manufacturer Part Number: hyb18t512161bf-33
• Description: 512-mbit X16 Gddr2 Dram
• Manufacturer: Infineon Technologies Corporation

3.5
The mode register stores the data for controlling the
various operating modes of DDR2 SDRAM. It programs
CAS latency, burst length, burst sequence, test mode,
DLL reset, Write Recovery (WR) and various vendor
specific options to make DDR2 SDRAM useful for
various applications. The default value of the mode
register is not defined, therefore the mode register must
be written after power-up for proper operation. The
mode register is written by asserting low on CS, RAS,
CAS, WE, BA[1:0], while controlling the state of
address pins A[13:0]. The DDR2 SDRAM should be in
all bank precharged (idle) mode with CKE already high
prior to writing into the mode register. The mode
register set command cycle time (
complete the write operation to the mode register. The
mode register contents can be changed using the same
Data Sheet
DDR2 SDRAM Mode Register Set (MRS)
t
MRD
) is required to
20
command and clock cycle requirements during normal
operation as long as all banks are in the precharged
state. The mode register is divided into various fields
depending on functionality. Burst length is defined by
A[2:0] with options of 4 and 8 bit burst length. Burst
address sequence type is defined by A3 and CAS
latency is defined by A[6:4]. A7 is used for test mode
and must be set to 0 for normal DRAM operation. A8 is
used for DLL reset. A[11:9] are used for write recovery
time (WR) definition for Auto-Precharge mode. With
address bit A12 two Power-Down modes can be
selected, a “standard mode” and a “low-power” Power-
Down mode, where the DLL is disabled. Address bit
A13 and all “higher” address bits have to be set to 0 for
compatibility with other DDR2 memory products with
higher memory densities.
512-Mbit Double-Data-Rate-Two SDRAM
HYB18T512161BF–22/25/28/33
Functional Description
05102005-C5U8-7TLE
Rev. 1.1, 2005-08