IC42S16100
Bank Active Command Interval
that bank within the ACT to PRE command period (tRAS
max). Also note that a precharge command cannot be
executed for an active bank before tRAS (min) has elapsed.
After a bank active command has been executed and the
trcd period has elapsed, read write (including auto-
precharge) commands can be executed for that bank.
When the selected bank is precharged, the period trp has
elapsed and the bank has entered the idle state, the bank
can be activated by executing the active command. If the
other bank is in the idle state at that time, the active
command can be executed for that bank after the period
tRRD has elapsed. At that point both banks will be in the
active state. When a bank active command has been
executed, a precharge command must be executed for
CLK
t
RRD
COMMAND
ACT 0
ACT 1
BANK ACTIVE (BANK 0)
BANK ACTIVE (BANK 1)
CLK
t
RCD
COMMAND
ACT 0
READ 0
BANK ACTIVE (BANK 0)
BANK ACTIVE (BANK 0)
CAS latency = 3
Clock Suspend
When the CKE pin is dropped from HIGH to LOW during a
read or write cycle, the IC42S16100 enters clock suspend
mode on the next CLK rising edge. This command reduces
the device power dissipation by stopping the device internal
clock. Clock suspend mode continues as long as the CKE
pin remains low. In this state, all inputs other than CKE pin
are invalid and no other commands can be executed. Also,
the device internal states are maintained. When the CKE
pin goes from LOW to HIGH clock suspend mode is
terminatedonthenextCLKrisingedgeanddeviceoperation
resumes.
The next command cannot be executed until the recovery
period (tCKA) has elapsed.
Since this command differs from the self-refresh command
described previously in that the refresh operation is not
performed automatically internally, the refresh operation
must be performed within the refresh period (tref). Thus the
maximum time that clock suspend mode can be held is just
under the refresh cycle time.
CLK
CKE
COMMAND
I/O
READ 0
DOUT 0
DOUT 1
DOUT 2
DOUT 3
READ (BANK 0)
CLOCK SUSPEND
CAS latency = 2, burst length = 4
Integrated Circuit Solution Inc.
35
DR024-0D 06/25/2004
ICSI [ INTEGRATED CIRCUIT SOLUTION INC ]
