Datasheet

Activate Command
The Activate command is used to open (or activate) a row in a particular bank for a subsequent access. The
value on the BG0 in x16 select the bank group; BA0-BA1 inputs selects the bank within the bank group, and
the address provided on inputs A0-A14 selects the row. This row remains active (or open) for accesses until a
precharge command is issued to that bank or a precharge all command is issued. A bank must be precharged
before opening a different row in the same bank.
Precharge Command
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 activation a specified time (t
RP
) 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. 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 is allowed if there is no open row
in that bank (idle state) or if the previously open row is already in the process of precharging. However, the
precharge period will be determined by the last Precharge command issued to the bank.
If A10 is high when Read or Write command is issued, then auto-precharge function is engaged. This feature
allows the precharge operation to be partially or completely hidden during burst read cycles (dependent upon
CAS latency) thus improving system performance for random data access. The RAS lockout circuit internally
delays the precharge operation until the array restore operation has been completed (t
RAS
satisfied) so that
the auto precharge command may be issued with any read. Auto-precharge is also implemented during Write
commands. The precharge operation engaged by the Auto precharge command will not begin until the last data
of the burst write sequence is properly stored in the memory array. The bank will be avaiable for a subsequent
row activation a specified time (t
RP
) after hidden Precharge command (AutoPrecharge) is issued to that bank.
AS4C256M16D4
Confidential
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Rev.1.0 Aug.2019