Pin Descriptions
The pin description table below is a comprehensive list of all possible pins for all DDR2
modules. All pins listed may not be supported on this module. See Pin Assignments for
information specific to this module.
Table 7: Pin Descriptions
Symbol Type Description
Ax Input
Address inputs: Provide the row address for ACTIVE commands, and the column ad-
dress and auto precharge bit (A10) for READ/WRITE commands, to select one location
out of the memory array in the respective bank. A10 sampled during a PRECHARGE
command determines whether the PRECHARGE applies to one bank (A10 LOW, bank
selected by BAx) or all banks (A10 HIGH). The address inputs also provide the op-code
during a LOAD MODE command. See the Pin Assignments Table for density-specific
addressing information.
BAx Input
Bank address inputs: Define the device bank to which an ACTIVE, READ, WRITE, or
PRECHARGE command is being applied. BA define which mode register (MR0, MR1,
MR2, and MR3) is loaded during the LOAD MODE command.
CKx,
CK#x
Input
Clock: Differential clock inputs. All control, command, and address input signals are
sampled on the crossing of the positive edge of CK and the negative edge of CK#.
CKEx Input
Clock enable: Enables (registered HIGH) and disables (registered LOW) internal circui-
try and clocks on the DDR2 SDRAM.
DMx, Input
Data mask (x8 devices only): DM is an input mask signal for write data. Input data
is masked when DM is sampled HIGH, along with that input data, during a write ac-
cess. Although DM pins are input-only, DM loading is designed to match that of the
DQ and DQS pins.
ODTx Input
On-die termination: Enables (registered HIGH) and disables (registered LOW) termi-
nation resistance internal to the DDR2 SDRAM. When enabled in normal operation,
ODT is only applied to the following pins: DQ, DQS, DQS#, DM, and CB. The ODT input
will be ignored if disabled via the LOAD MODE command.
Par_In Input
Parity input: Parity bit for Ax, RAS#, CAS#, and WE#.
RAS#, CAS#, WE# Input
Command inputs: RAS#, CAS#, and WE# (along with S#) define the command being
entered.
RESET# Input
Reset: Asynchronously forces all registered outputs LOW when RESET# is LOW. This
signal can be used during power-up to ensure that CKE is LOW and DQ are High-Z.
S#x Input
Chip select: Enables (registered LOW) and disables (registered HIGH) the command
decoder.
SAx Input
Serial address inputs: Used to configure the SPD EEPROM address range on the I
2
C
bus.
SCL Input
Serial clock for SPD EEPROM: Used to synchronize communication to and from the
SPD EEPROM on the I
2
C bus.
CBx I/O
Check bits. Used for system error detection and correction.
DQx I/O
Data input/output: Bidirectional data bus.
DQSx,
DQS#x
I/O
Data strobe: Travels with the DQ and is used to capture DQ at the DRAM or the con-
troller. Output with read data; input with write data for source synchronous opera-
tion. DQS# is only used when differential data strobe mode is enabled via the LOAD
MODE command.
128MB, 256MB, 512MB (x64, SR) 240-Pin DDR2 SDRAM UDIMM
Pin Descriptions
PDF: 09005aef80ed6fda
htf4c16_32_64x64ay – Rev. H 3/10 EN
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© 2003 Micron Technology, Inc. All rights reserved.
