WED3DL644V
White Electronic Designs
CURRENT STATE TRUTH TABLE (CONT.)
Command
RAS# CAS# WE# BA0-1
Current State
Action
Notes
A11,
A10/AP-A0
CE#
Description
L
L
L
L
L
L
L
L
H
L
L
L
L
L
L
L
L
H
L
L
L
L
L
H
H
L
L
H
L
H
L
H
L
H
X
L
H
L
H
L
H
L
H
X
OP Code
Mode Register Set
Auto or Self Refresh
Precharge
Bank Activate
Write
ILLEGAL
ILLEGAL
ILLEGAL
ILLEGAL
ILLEGAL
X
X
BA
BA
BA
X
X
X
L
Row Address
Column
Column
Refreshing
H
H
H
H
X
L
L
L
L
H
H
H
H
X
L
Read
ILLEGAL
H
H
X
L
X
X
X
Burst Termination
No Operation
Device Deselect
Mode Register Set
Auto or Self Refresh
Precharge
No Operation; Idle after trc
No Operation; Idle after trc
No Operation; Idle after trc
Load mode register
ILLEGAL
X
X
OP Code
L
X
X
BA
BA
BA
X
X
X
H
H
L
ILLEGAL
ILLEGAL
ILLEGAL
ILLEGAL
Row Address
Column
Column
Bank Activate
Write
Mode Register
Accessing
L
Read
H
H
X
X
X
X
Burst Termination
No Operation
Device Deselect
ILLEGAL
X
X
No Operation; Idle after two clock cycles
No Operation; Idle after two clock cycles
Notes:
1.
2.
3.
4.
CKE is assumed to be active (high) in the previous cycle for all entries. The Current State is the state of the bank that the command is being applied to.
Both Banks must be idle otherwise it is an illegal action.
If CKE is active (high) the SDRAM starts the Auto (CBR) Refresh operation, if CKE is inactive (low) then the Self Refresh mode is entered.
The Current State refers only refers to one of the banks, if BA selects this bank then the action is illegal. If BA selects the bank not being referenced by the Current State then
the action may be legal depending on the state of that bank.
5.
6.
7.
8.
9.
If CKE is inactive (low) than the Power Down mode is entered, otherwise there is a No Operation.
The minimum and maximum Active time (tRAS) must be satisfied.
The RAS# to CAS# Delay (tRCD) must occur before the command is given.
Address A10 is used to determine if the Auto Precharge function is activated.
The command must satisfy any bus contention, bus turn around, and/or write recovery requirements.
August 2005
Rev. 6
11
White Electronic Designs Corporation • (602) 437-1520 • www.wedc.com
WEDC [ WHITE ELECTRONIC DESIGNS CORPORATION ]
