WEDPNF8M722V-1212BC 查看數據表（PDF） - White Electronic Designs Corporation
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WEDPNF8M722V-1212BC
White Electronic Designs Corporation
WEDPNF8M722V-1212BC Datasheet PDF : 43 Pages
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White Electronic Designs WEDPNF8M722V-XBX
TABLE 3 TRUTH TABLE - COMMANDS AND DQM OPERATION (NOTE 1)
NAME (FUNCTION)
CS
RAS
CAS
WE DQM
ADDR
I/Os
COMMAND INHIBIT (NOP)
H
X
X
X
X
X
X
NO OPERATION (NOP)
L
H
H
H
X
X
X
ACTIVE (Select bank and activate row) ( 3)
L
L
H
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
L/H 8
Bank/Col
Valid
BURST TERMINATE
L
H
H
L
X
X
Active
PRECHARGE (Deactivate row in bank or banks) ( 5)
L
L
H
L
X
Code
X
AUTO REFRESH or SELF REFRESH (Enter self refresh mode) (6, 7)
L
L
L
H
X
X
X
LOAD MODE REGISTER (2)
L
L
L
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 define the op-code written to the Mode Register.
3. A0-11 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).
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 dese-
lected. Operations already in progress are not affected.
BA0, BA1 inputs selects the bank, and the address pro-
vided on inputs A0-11 selects the row. This row remains
active (or open) for accesses until a PRECHARGE command
is issued to that bank. A PRECHARGE command must be
issued before opening a different row in the same bank.
NO OPERATION (NOP)
The NO OPERATION (NOP) command is used to perform a
NOP to an SDRAM which is selected (CS is LOW). This pre-
vents 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 Definition 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.
READ
The READ command is used to initiate a burst read access
to an active row. The value on the BA0, BA1 inputs selects
the bank, and the address provided on inputs A0-8 se-
lects 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. Read data appears on the I/Os sub-
ject to the logic level on the DQM inputs two clocks earlier.
If a given DQM signal was registered HIGH, the correspond-
ing I/Os will be High-Z two clocks later; if the DQM signal
was registered LOW, the I/Os will provide valid data.
ACTIVE
The ACTIVE command is used to open (or activate) a row in
a particular bank for a subsequent access. The value on the
WRITE
The WRITE command is used to initiate a burst write access
to an active row. The value on the BA0, BA1 inputs selects
the bank, and the address provided on inputs A0-8 selects
11
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