EMD12324PV Emlsi Inc., EMD12324PV Datasheet - Page 19

• Manufacturer Part Number: EMD12324PV
• Description: 512m 16m X 32 Mobile Ddr Sdram
• Manufacturer: Emlsi Inc.

Preliminary
EMD12324PV
512M: 16M x 32 Mobile DDR SDRAM
Commands
DESELECT
The DESELECT function (CSB HIGH) prevents new commands from being executed by the Mobile DDR SDRAM. The
Mobile DDR SDRAM is effectively deselected. Operations already in progress are not affected.
NO OPERATION (NOP)
The NO OPERATION (NOP) command is used to instruct the selected DDR SDRAM to perform a NOP (CSB = LOW,
RASB = CASB = WEB = HIGH). This prevents unwanted commands from being registered during idle or wait states.
Operations already in progress are not affected.
LOAD MODE REGISTER
The mode register is loaded via inputs A0-A12, BA0, BA1. The LOAD MODE REGISTER and LOAD EXTENDED
MODE REGISTER commands can only be issued when all banks are idle, and a subsequent executable command
cannot be issued until tMRD is met.
The values of the mode register and extended mode register will be retained even when exiting deep power-down.
ACTIVE
The ACTIVE command is used to open (or activate) a row in a particular bank for a subsequent access. The value on
the BA0, BA1 inputs selects the bank, and the address provided on inputs A0-A12 selects the row. This row remains
active (or open) for accesses until a PRECHARGE command is issued to that bank. A PRECHARGE command must
be issued before opening a different row in the same bank.
READ
The READ command is used to initiate a burst read access to an active row. The value on the BA0, BA1 inputs selects
the bank, and the address provided on inputs A0-A8 selects the starting column location. The value on input A10
determines whether or not auto precharge is used. If auto precharge is selected, the row being accessed will be pre-
charged at the end of the READ burst; if auto precharge is not selected, the row will remain open for subsequent
accesses.
WRITE
The WRITE command is used to initiate a burst write access to an active row. The value on the BA0, BA1 inputs
selects the bank, and the address provided on inputs A0-A8 selects the starting column location. The value on input
A10 determines whether or not auto precharge is used. If auto precharge is selected, the row being accessed will be
precharged at the end of the WRITE burst; if auto precharge is not selected, the row will remain open for subsequent
accesses. Input data appearing on the DQs is written to the memory array subject to the DM input logic level appearing
coincident with the data. If a given DM signal is registered LOW, the corresponding data will be written to memory; if
the DM signal is registered HIGH, the corresponding data inputs will be ignored, and a WRITE will not be executed to
that byte/column location.
PRECHARGE
The PRECHARGE command is used to deactivate the open row in a particular bank or the open row in all banks. The
bank(s) will be available for a subsequent row access a specified time (tRP) after the precharge command is issued.
Except in the case of concurrent auto precharge, where a READ or WRITE command to a different bank is allowed as
long as it does not interrupt the data transfer in the current bank and does not violate any other timing parameters.
Input A10 determines whether one or all banks are to be precharged, and in the case where only one bank is to be pre-
charged, inputs BA0, BA1 select the bank. Otherwise BA0, BA1 are treated as “Don’t Care”. Once a bank has been
precharged, it is in the idle state and must be activated prior to any READ or WRITE commands being issued to that
bank. A PRECHARGE command will be treated as a NOP if there is no open row in that bank (idle state), or if the pre-
viously open row is already in the process of precharging.
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