is43lr32200b-6bl Integrated Silicon Solution, Inc., is43lr32200b-6bl Datasheet - Page 13

• Manufacturer Part Number: is43lr32200b-6bl
• Description: 512k X 32bits X 4banks Mobile Ddr Sdram
• Manufacturer: Integrated Silicon Solution, Inc.

IS43/46LR32200B
Advanced Information
Commands
The following COMMANDS Truth Table and DM Operation Truth Table provide quick reference of available commands. This is followed by a
written description of each command.
Deselect
The DESELECT function (/CS 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 (/CS = LOW, /RAS = /CAS = /WE =
HIGH). This prevents unwanted commands from being registered during idle or wait states. Operations already in progress are not affected.
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–A10 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–A7 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 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-A7 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 precharged, inputs BA0, BA1select 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 previously open row is already in the process of
precharging.
Rev. 00A | Feb. 2011
13
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