256Mb: x4, x8, x16 SDRAM
Truth Tables
Table 16: Truth Table – Current State Bank n, Command to Bank m
Notes 1–6 apply to all parameters and conditions
Current State
CS# RAS# CAS# WE# Command/Action
Notes
Any
H
L
X
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
X
H
X
L
X
H
X
H
L
X
H
X
H
H
L
COMMAND INHIBIT (NOP/continue previous operation)
NO OPERATION (NOP/continue previous operation)
Any command otherwise supported for bank m
ACTIVE (select and activate row)
READ (select column and start READ burst)
WRITE (select column and start WRITE burst)
PRECHARGE
Idle
Row activating, active, or
precharging
H
H
L
7
7
L
H
H
L
L
Read
L
H
H
L
ACTIVE (select and activate row)
READ (select column and start new READ burst)
WRITE (select column and start WRITE burst)
PRECHARGE
(auto precharge disabled)
H
H
L
7, 10
7, 11
9
L
H
H
L
L
Write
L
H
H
L
ACTIVE (select and activate row)
READ (select column and start READ burst)
WRITE (select column and start new WRITE burst)
PRECHARGE
(auto precharge disabled)
H
H
L
7, 12
7, 13
9
L
H
H
L
L
Read
L
H
H
L
ACTIVE (select and activate row)
READ (select column and start new READ burst)
WRITE (select column and start WRITE burst)
PRECHARGE
(with auto precharge)
H
H
L
7, 8, 14
7, 8, 15
9
L
H
H
L
L
Write
(with auto precharge)
L
H
H
L
ACTIVE (select and activate row)
READ (select column and start READ burst)
WRITE (select column and start new WRITE burst)
PRECHARGE
H
H
L
7, 8, 16
7, 8, 17
9
L
H
L
1. This table applies when CKEn-1 was HIGH and CKEn is HIGH (Table 17 (page 41)), and
after tXSR has been met (if the previous state was self refresh).
Notes:
2. This table describes alternate bank operation, except where noted; for example, the cur-
rent state is for bank n and the commands shown can be issued to bank m, assuming
that bank m is in such a state that the given command is supported. Exceptions are cov-
ered below.
3. Current state definitions:
Idle: The bank has been precharged, and tRP has been met.
Row active: A row in the bank has been activated, and tRCD has been met. No data
bursts/accesses and no register accesses are in progress.
Read: A READ burst has been initiated, with auto precharge disabled, and has not yet
terminated or been terminated.
Write: A WRITE burst has been initiated, with auto precharge disabled, and has not yet
terminated or been terminated.
PDF: 09005aef8091e6d1
256Mb_sdr.pdf - Rev. R 10/12 EN
Micron Technology, Inc. reserves the right to change products or specifications without notice.
39
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