MB81P643287 Datasheet, PDF (24/65 Pages) Fujitsu Component Limited. – 8 x 256K x 32 BIT, FCRAMTM CORE BASED DOUBLE DATA RATE SDRAM

MB81P643287-50/-60
BURST STOP COMMAND (BST)
The Burst Stop command (BST) terminates the burst read operation except for a case that Auto-precharge option
is asserted. When the BST command is issued during the burst read operation, the all output buffers, DQs and
DQS0 to DQS3, will turn to High-Z state after some latencies that to be matched with programmed CAS latency
and internal bank state remains active state.
In a case of terminating the burst write operation, the BST command should not be issued at any time during
burst write operation. Refer to previous page for the write interrupt and termination rule.
PRECHARGE AND PRECHARGE OPTION (PRE, PALL)
The DDR SDRAM memory core is the same as conventional DRAMs’, requiring precharge and refresh opera-
tions. Precharge rewrites the bit line and to reset the internal Row address line and is executed by the precharge
operation (PRE or PALL). With the precharge operation, DDR SDRAM will automatically be in standby state
after specified precharge time (lRP, lRPA).
The precharged bank is selected by combination of AP and bank address (BA) when precharge command is
issued. If AP = High, all banks are precharged regardless of BA (PALL command). If AP = Low, a bank to be
selected by BA is precharged (PRE command).
The auto-precharge enters precharge mode at the end of burst mode of read or write without Precharge command
issue. This auto-precharge is entered by AP = High when a Read (READ) or Write (WRIT) command is issued.
Applying BST is illegal if the Auto-precharge option is used.
Refer to “sFUNCTION TRUTH TABLE”.
AUTO-REFRESH (REF)
Auto-refresh uses the internal refresh address counter. The MB81P643287 Auto-refresh command (REF) au-
tomatically generates Bank Active and Precharge command internally. All banks of SDRAM should be pre-
charged prior to the Auto-refresh command. The Auto-refresh command should also be issued within every 8
µs period.
SELF-REFRESH ENTRY (SELF)
Self-refresh function provides automatic refresh by an internal timer as well as Auto-refresh and will continue
the refresh operation until cancelled by SELFX.
The Self-refresh mode is entered by applying an Auto-refresh command in conjunction with CKE = Low (SELF).
Once MB81P643287 enters the self-refresh mode, all inputs except for CKE can be either logic high or low level
state and outputs will be in a High-Z state. During Self-refresh mode, CKE = Low should be maintained. SELF
command should only be issued after last read data has been appeared on DQ.
Note: When the burst refresh method is used, a total of 4096 auto-refresh commands within 4 ms must be asserted
prior to the self-refresh mode entry.
SELF-REFRESH EXIT (SELFX)
To exit Self-refresh mode, CKE must bring to High for at least 2 clock cycles together with NOP condition.
Refer to Timing Diagram for the detail procedure. It is recommended to issue at least one Auto-refresh command
just after the lRFC period to avoid the violation of refresh period.
WARNING: A stable clock for lSCD period with a constant duty cycle must be supplied prior to applying any read
command to insure the DLL is locked against the latest device conditions.
Note: When the burst refresh method is used, a total of 4096 auto-refresh commands within 4 ms must be asserted
both before the self-refresh entry and after the self-refresh exit.
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