46DR83200A Datasheet, PDF (43/48 Pages) Integrated Silicon Solution, Inc – 32Mx8, 16Mx16 DDR2 DRAM

IS43/46DR83200A, IS43/46DR16160A
DESELECT
The DESELECT function (CS HIGH) prevents new commands from being executed by the DDR2 SDRAM. The DDR2
SDRAM is effectively deselected. Operations already in progress are not affected. DESELECT is also referred to as
COMMAND INHIBIT.
NO OPERATION (NOP)
The NO OPERATION (NOP) command is used to instruct the selected DDR2 SDRAM to perform a NOP (CS is LOW;
RAS, CAS, and WE are HIGH). This prevents unwanted commands from being registered during idle or wait states.
Operations already in progress are not affected.
MODE REGISTER SET (MRS or EMRS)
The mode registers are loaded via bank address and address inputs. The bank address balls determine which mode
register will be programmed. See sections on Mode Register and Extended Mode Register. The MRS and EMRS
commands can only be issued when all banks are idle, and a subsequent executable command cannot be issued until
tMRD is met.
ACTIVATE
The ACTIVATE command is used to open (or activate) a row in a particular bank for a subsequent access. The value
on the bank address inputs determines the bank, and the address inputs select 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 bank address inputs
determine the bank, and the address provided on address inputs A0–A9 (x8) or A0–A8 (x16) 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.
DDR2 SDRAM also supports the AL feature, which allows a READ or WRITE command to be issued prior to tRCD
(MIN) by delaying the actual registration of the READ/WRITE command to the internal device by AL clock cycles.
WRITE
The WRITE command is used to initiate a burst write access to an active row. The value on the bank select inputs
selects the bank, and the address provided on inputs A0–A9 (x8) or A0–A8 (x16) 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.
DDR2 SDRAM also supports the AL feature, which allows a READ or WRITE command to be issued prior to tRCD
(MIN) by delaying the actual registration of the READ/WRITE command to the internal device by AL clock cycles.
Input data appearing on the DQ 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.
Integrated Silicon Solution, Inc. — www.issi.com
43
Rev. D
08/16/2012