A48P3616A
Functional Description
Initialization
The 128Mb DDR SDRAM is a high-speed CMOS, dynamic
random-access memory containing 134,217,728 bits. The
128Mb DDR SDRAM is internally configured as a quad-bank
DRAM.
The following relationships must be followed: VDDQ is driven
after or with VDD such that VDDQ < VDD + 0.3V VTT is driven
after or with VDDQ such that VTT < VDDQ + 0.3V VREF is driven
after or with VDDQ such that VREF < VDDQ + 0.3V
The 128Mb DDR SDRAM uses
a
double-data-rate
The DQ and DQS outputs are in the High-Z state, where they
remain until driven in normal operation (by a read access).
After all power supply and reference voltages are stable, and
the clock is stable, the DDR SDRAM requires a 200μs delay
prior to applying an executable command.
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 128Mb DDR SDRAM 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.
Once the 200μs delay has been satisfied, a Deselect or
NOP command should be applied, and CKE must be brought
HIGH. Following the NOP command, a Precharge ALL
command must be applied. Next a Mode Register Set
command must be issued for the Extended Mode Register,
to enable the DLL, then a Mode Register Set command must
be issued for the Mode Register, to reset the DLL, and to
program the operating parameters. 200 clock cycles are
required between the DLL reset and any read command. A
Precharge ALL command should be applied, placing the
device in the “all banks idle” state
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 (BA0, BA1 select the bank; A0-A11 select the row).
The address bits registered coincident with the Read or Write
command are used to select the starting column location for
the burst access.
Once in the idle state, two auto refresh cycles must be
performed. Additionally, a Mode Register Set command for
the Mode Register, with the reset DLL bit deactivated (i.e. to
program operating parameters without resetting the DLL)
must be performed. Following these cycles, the DDR
SDRAM is ready for normal operation.
Prior to normal operation, the DDR SDRAM must be
initialized. The following sections provide detailed information
covering device initialization, register definition, command
descriptions and device operation.
DDR SDRAM’s may be reinitialized at any time during
normal operation by asserting a valid MRS command to
either the base or extended mode registers without affecting
the contents of the memory array. The contents of either the
mode register or extended mode register can be modified at
any valid time during device operation without affecting the
state of the internal address refresh counters used for device
refresh.
PRELIMINARY (July, 2010, Version 0.0)
5
AMIC Technology, Corp.
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