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WEDPN16M64VR-XB2X
7
White Electronic Designs Corporation (602) 437-1520 www.whiteedc.com
White Electronic Designs
January 2005
Rev. 0
COMMANDS
The Truth Table provides a quick reference of available
commands. This is followed by a written description of each
command. Three additional Truth Tables appear following
the Operation section; these tables provide current state/
next state information.
INPUTS
OUTPUT
OE#
LE#
CLK
A
Y
H
XXX
Z
LL
X
L
LL
X
H
LH
I
L
HIH
H
L
H
L or H
X
Y0(1)
NOTES: 1. Output level before the indicated steady-state input conditions were
established.
REGISTER FUNCTION TABLE
COMMAND INHIBIT
The COMMAND INHIBIT function prevents new commands
from being executed by the SDRAM, regardless of whether
the CLK signal is enabled. The SDRAM is effectively
deselected. Operations already in progress are not
affected.
NO OPERATION (NOP)
The NO OPERATION (NOP) command is used to perform
a NOP to an SDRAM which is selected (CS is LOW). This
prevents unwanted commands from being registered during
idle or wait states. Operations already in progress are not
affected.
LOAD MODE REGISTER
The Mode Register is loaded via inputs A0-11. See Mode
Register heading in the Register Denition section. The
LOAD MODE REGISTER command can only be issued
when all banks are idle, and a subsequent executable
command cannot be issued until tMRD is met.
TRUTH TABLE — COMMANDS AND DQM OPERATION (NOTE 1)
NAME (FUNCTION)
CS#
RAS#
CAS#
WE#
DQM
ADDR
I/Os
COMMAND INHIBIT (NOP)
H
X
NO OPERATION (NOP)
L
H
X
ACTIVE (Select bank and activate row) ( 3)
L
H
X
Bank/Row
X
READ (Select bank and column, and start READ burst) (4)
L
H
L
H
L/H 8
Bank/Col
X
WRITE (Select bank and column, and start WRITE burst) (4)
L
H
L
L/H 8
Bank/Col
Valid
BURST TERMINATE
L
H
L
X
Active
PRECHARGE (Deactivate row in bank or banks) ( 5)
L
H
L
X
Code
X
AUTO REFRESH or SELF REFRESH (Enter self refresh mode) (6, 7)
L
H
X
LOAD MODE REGISTER (2)
L
X
Op-Code
X
Write Enable/Output Enable (8)
–
L
–
Active
Write Inhibit/Output High-Z (8)
–
H
–
High-Z
NOTES:
1. CKE is HIGH for all commands shown except SELF REFRESH.
2. A0-11 dene the op-code written to the Mode Register.
3. A0-12 provide row address, and BA0, BA1 determine which bank is made active.
4. A0-8 provide column address; A10 HIGH enables the auto precharge feature
(nonpersistent), while A10 LOW disables the auto precharge feature; BA0, BA1
determine which bank is being read from or written to.
5. A10 LOW: BA0, BA1 determine the bank being precharged. A10 HIGH: All banks
precharged and BA0, BA1 are “Don’t Care.”
6. This command is AUTO REFRESH if CKE is HIGH; SELF REFRESH if CKE is
LOW.
7. Internal refresh counter controls row addressing; all inputs and I/Os are “Don’t Care”
except for CKE.
8. Activates or deactivates the I/Os during WRITEs (zero-clock delay) and READs
(two-clock delay).