IS42S16400E Datasheet, PDF (18/55 Pages) Integrated Silicon Solution, Inc – 1 Meg Bits x 16 Bits x 4 Banks (64-MBIT) SYNCHRONOUS DYNAMIC RAM

IS42S16400E
CAS Latency
The CAS latency is the delay, in clock cycles, between
the registration of a READ command and the availability of
the first piece of output data. The latency can be set to two or
three clocks.
If a READ command is registered at clock edge n, and
the latency is m clocks, the data will be available by clock
edge n + m. The DQs will start driving as a result of the
clock edge one cycle earlier (n + m - 1), and provided that
the relevant access times are met, the data will be valid by
clock edge n + m. For example, assuming that the clock
cycle time is such that all relevant access times are met,
if a READ command is registered at T0 and the latency
is programmed to two clocks, the DQs will start driving
after T1 and the data will be valid by T2, as shown in CAS
Latency diagrams. The Allowable Operating Frequency
table indicates the operating frequencies at which each
CAS latency setting can be used.
Reserved states should not be used as unknown operation
or incompatibility with future versions may result.
Operating Mode
The normal operating mode is selected by setting M7 and M8
to zero; the other combinations of values for M7 and M8 are
reserved for future use and/or test modes. The programmed
burst length applies to both READ and WRITE bursts.
Test modes and reserved states should not be used be-
cause unknown operation or incompatibility with future
versions may result.
Write Burst Mode
When M9 = 0, the burst length programmed via M0-M2
applies to both READ and WRITE bursts; when M9 = 1,
the programmed burst length applies to READ bursts, but
write accesses are single-location (nonburst) accesses.
CAS Latency
Allowable Operating Frequency (MHz)
Speed
CAS Latency = 2
CAS Latency = 3
6 ­133
166
7
133
143
CAS Latency
T0
T1
T2
T3
CLK
COMMAND
DQ
READ
NOP
NOP
tAC
DOUT
tLZ
tOH
CAS Latency - 2
T0
T1
T2
T3
T4
CLK
COMMAND READ
DQ
NOP
NOP
tAC
tLZ
CAS Latency - 3
NOP
DOUT
tOH
DON'T CARE
UNDEFINED
18
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Rev.  C
08/07/09