IS42S81600D Datasheet, PDF (27/62 Pages) Integrated Silicon Solution, Inc – 16Meg x 8, 8Meg x16 128-MBIT SYNCHRONOUS DRAM

IS42S81600D, IS42S16800D
CHIP OPERATION
BANK/ROW ACTIVATION
Before any READ or WRITE commands can be issued to a
bank within the SDRAM, a row in that bank must be “opened.”
This is accomplished via the ACTIVE command, which
selects both the bank and the row to be activated (see
Activating Specific Row Within Specific Bank).
After opening a row (issuing an ACTIVE command), a
READ or WRITE command may be issued to that row,
subject to the tRCD specification. Minimum tRCD should be
divided by the clock period and rounded up to the next whole
number to determine the earliest clock edge after the
ACTIVE command on which a READ or WRITE command
can be entered. For example, a tRCD specification of 18ns
with a 125 MHz clock (8ns period) results in 2.25 clocks,
rounded to 3. This is reflected in the following example,
which covers any case where 2 < [tRCD (MIN)/tCK] ≤ 3. (The
same procedure is used to convert other specification limits
from time units to clock cycles).
A subsequent ACTIVE command to a different row in the
same bank can only be issued after the previous active row
has been “closed” (precharged). The minimum time interval
between successive ACTIVE commands to the same bank
is defined by tRC.
A subsequent ACTIVE command to another bank can be
issued while the first bank is being accessed, which results
in a reduction of total row-access overhead. The minimum
time interval between successive ACTIVE commands to
different banks is defined by tRRD.
ACTIVATING SPECIFIC ROW WITHIN SPE-
CIFIC BANK
CLK
HIGH
CKE
CS
RAS
CAS
WE
A0-A11
BA0, BA1
ROW ADDRESS
BANK ADDRESS
EXAMPLE: MEETING TRCD (MIN) WHEN 2 < [TRCD (MIN)/TCK] ≤ 3
T0
T1
CLK
COMMAND ACTIVE
NOP
tRCD
T2
T3
T4
NOP
READ or
WRITE
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Integrated Silicon Solution, Inc. — www.issi.com
27
Rev. E
07/28/08