12
EMD28164PA
128M: 8M x 16 Mobile DDR SDRAM
Rev 1.0
Functional Description
The 128Mb Mobile DDR SDRAM is a high-speed CMOS, dynamic random-access memory containing 134,217,728-
bits. It is internally configured as a quad-ba nk DRAM. Each of the 33,554,432-bit banks is organized as 4,096 rows by
512 columns by 16 bits.
The 128Mb Mobile DDR 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 balls. single read or write access for the 128Mb Mobile 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 balls.
Read and write accesses to the Mobile DDR SDRAM are burst oriented; accesses start at a selected location and con-
tinue 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 se lect 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 start-
ing column location for the burst access.
It should be note d that the DLL signal that is typically used on standard DDR devices is not necessary on the Mobile
DDR SDRAM. It has been omitted to save power. Prior to no rmal operation, the Mobile DDR SDRAM must b e initial-
ized. The following sections provide detailed information covering device initialization, register definition, command
descriptions and device operation.
Initialization
Mobile DDR SDRAMs must be powere d up and initialized in a predefi ned mann er. Operational pro cedures other than
those specified may result in undefined op eration. If there is an interruption to the devi ce power, the ini tialization rou-
tine should be followed to ensure proper fu nctionality of the Mobile DDR SDRAM. The clock stop feature is not avail-
able until the device has been properly initi alized.
To properly initialize the Mobile DDR SDRAM, this sequence must be followed:
1. To prevent device latch-up, it is recommended the core power (VDD) and I/O power (VDDQ) be from the same
power source and brought up simultaneously. If separate power sources are used, VDD must lead VDDQ.
2. Once power supply voltages are stable and the CKE has been driven HIGH, it is safe to apply the clock.
3. Once the clock is stable, a 200µs (minimum) delay is required by the Mobile DDR SDRAM prior to applying an exe
cutable command. During this time, NOP or DESELECT commands must be issued on the command bus.
4. Issue a PRECHARGE ALL command.
5. Issue NOP or DESELECT commands for at least tRP time.
6. Issue an AUTO REFRESH command followed by NOP or DESELECT commands for at least tRFC time. Issue a
second AUTO REFRESH command followed by NOP or DESELECT commands for at least tRFC time. As part of
the initialization sequence, two AUTO REFRESH commands must be issued. Typically, both of these com
mands are issued at this stage as described above. Alternately, the second AUTO-REFRESH command and NOP
or DESELECT sequence can be issued between steps 10 and 11.
7. Using the LOAD MODE REGISTER command, load the standard mode register as desired.
8. Issue NOP or DESELECT commands for at least tMRD time.
9. Using the LOAD MODE REGISTER command, load the extended mode register to the desired operating modes.
Note that the sequence in which the standard and extended mode registers are programmed is not critical.
10. Issue NOP or DESELECT commands for at least tMRD time.
11. The Mobile DDR SDRAM has been properly initialized and is ready to receive any va lid command.