EDJ1108BABG, EDJ1116BABG
Read Command [READ, RDS4, RDS8, READA, RDAS4, RDAS8]
The read command is used to initiate a burst read access to an active row. The values on the BA inputs select the
bank, and the address provided on column address inputs 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.
Write Command [WRIT, WRS4, WRS8, WRITA, WRAS4, WRAS8]
The write command is used to initiate a burst write access to an active row. The values on the BA inputs select the
bank, and the address provided on column address inputs 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. 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.
Precharge Command [PRE, PALL]
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 access a specified time (tRP) after the precharge command is issued.
Input A10 determines whether one or all banks are to be precharged, and in the case where only one bank is to be
precharged, inputs BA select the bank. Otherwise BA are treated as "Don't Care." 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 will be treated as a NOP if there is no open row in that bank (idle state), or if the
previously open row is already in the process of precharging.
Auto precharge Command [READA, WRITA]
Before a new row in an active bank can be opened, the active bank must be precharged using either the precharge
command or the auto precharge function. When a read or a write command is given to the DDR3 SDRAM, the /CAS
timing accepts one extra address, column address A10, to allow the active bank to automatically begin precharge at
the earliest possible moment during the burst read or write cycle. If A10 is low when the read or write command is
issued, then normal read or write burst operation is executed and the bank remains active at the completion of the
burst sequence. If A10 is high when the read or write command is issued, then the auto precharge function is
engaged. During auto precharge, a read command will execute as normal with the exception that the active bank
will begin to precharge on the rising edge which is /CAS latency (CL) clock cycles before the end of the read burst.
(This timing is equal to the rising edge which is (AL* + BL/2) cycles later from the read with auto precharge
command.)
Auto precharge can also be 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.
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 tRAS lockout circuit internally
delays the Precharge operation until the array restore operation has been completed so that the auto precharge
command may be issued with any read or write command.
Note: AL (Additive Latency), refer to Posted /CAS description in the Register Definition section.
Auto-Refresh Command [REF]
Auto-refresh is used during normal operation of the DDR3 SDRAM and is analogous to /CAS-before-/RAS (CBR)
refresh in FPM/EDO DRAM. This command is nonpersistent, so it must be issued each time a refresh is required.
The addressing is generated by the internal refresh controller. This makes the address bits a "Don't Care" during an
auto-refresh command.
A maximum of eight auto-refresh commands can be posted to any given DDR3, meaning that the maximum absolute
interval between any auto-refresh command and the next auto-refresh command is 9 × tREFI. This maximum
absolute interval is to allow DDR3 output drivers and internal terminators to automatically recalibrate compensating
for voltage and temperature changes.
Data Sheet E1248E40 (Ver. 4.0)
68
ELPIDA [ ELPIDA MEMORY ]
