4
Integrated Silicon Solution, Inc. — 1-800-379-4774
Rev. 00A
07/11/05
ISSI
®
IS43R16800A
PIN FUNCTIONS
Symbol Type Function (In Detail)
A0-A11 Input Pin Address inputs are sampled during several commands. During an Active
command, A0-A11 select a row to open. During a Read or Write command,
A0-A8 select a starting column for a burst. During a Pre-charge command,
A10 determines whether all banks are to be pre-charged, or a single bank.
During a Load Mode Register command, the address inputs select an
operating mode.
BA0, BA1 Input Pin Bank Address inputs are used to select a bank during Active, Pre-charge,
Read, or Write commands. During a Load Mode Register command, BA0
and BA1 are used to select between the Base or Extended Mode Register
CAS Input Pin CAS is Column Access Strobe, which is an input to the device command
along with RAS and WE. See “Command Truth Table” for details.
CKE Input Pin Clock Enable: CKE High activates and CKE Low de-activates internal clock
signals and input/output buffers. When CKE goes Low, it can allow Self
Refresh, Pre-charge Power Down, and Active Power Down. CKE must be
High during entire Read and Write accesses. Input buffers except CLK,
CLK, and CKE are disabled during Power Down. CKE uses an SSTL 2
input, but will detect a LVCMOS Low level after VDD is applied.
CLK, CLK Input Pin All address and command inputs are sampled on the rising edge of the
clock input CLK and the falling edge of the differential clock input CLK.
Output data is referenced from the crossings of CLK and CLK.
CS Input Pin The Chip Select input enables the Command Decoding block of the device.
When CS is disabled, a NOP occurs. See “Command Truth Table” for
details. Multiple DDR SDRAM devices can be managed with CS.
LDM, UDM Input Pin These are the Data Mask inputs. During a Write operation, the Data Mask
input allows masking of the data bus. DM is sampled on each edge of DQS.
There are two Data Mask input pins for the x16 DDR SDRAM. Each input
applies to DQ0-DQ7, or DQ8-DQ15.
LDQS, UDQS Input/Output Pin These are the Data Strobe inputs. The Data Strobe is used for data capture.
During a Read operation, the DQS output signal from the device is edge-
aligned with valid data on the data bus. During a Write operation, the DQS
input should be issued to the DDR SDRAM device when the input values on
DQ inputs are stable. There are two Data Strobe pins for the x16 DDR
SDRAM. Each of the two Data Strobe pins applies to DQ0-DQ7, or DQ8-
DQ15.
DQ0-DQ15 Input/Output Pin The pins DQ0 to DQ15 represent the data bus. For Write operations, the
data bus is sampled on Data Strobe. For Read operations, the data bus is
sampled on the crossings of CK and CK.
NC — No Connect: This pin should be left floating. These pins could be used for
256Mbit or higher density DDR SDRAM.
RAS Input Pin RAS is Row Access Strobe, which is an input to the device command
along with CAS and WE. See “Command Truth Table” for details.
WE Input Pin WE is Write Enable, which is an input to the device command along with
RAS and CAS. See “Command Truth Table” for details.
VDDQ Power Supply Pin VDDQ is the output buffer power supply.
VDD Power Supply Pin VDD is the device power supply.
VREF Power Supply Pin VREF is the reference voltage for SSTL 2.
VSSQ Power Supply Pin VSSQ is the output buffer ground.
VSS Power Supply Pin VSS is the device ground.
