PRELIMINARY
256Mb: x32
SDRAM
PIN DESCRIPTIONS
PIN NUMBERS
68
SYMBOL TYPE
CLK
Input
DESCRIPTION
Clock: CLK is driven by the system clock. All SDRAM input signals
are sampled on the positive edge of CLK. CLK also increments
the internal burst counter and controls the output registers.
Clock Enable: CKE activates (HIGH) and deactivates (LOW) the
CLK signal. Deactivating the clock provides PRECHARGE POWER-
DOWN and SELF REFRESH operation (all banks idle), ACTIVE
POWER-DOWN (row active in any bank) or CLOCK SUSPEND
operation (burst/access in progress). CKE is synchronous except
after the device enters power-down and self refresh modes,
where CKE becomes asynchronous until after exiting the same
mode. The input buffers, including CLK, are disabled during
power-down and self refresh modes, providing low standby
power. CKE may be tied HIGH.
Chip Select: CS# enables (registered LOW) and disables (regis-
tered HIGH) the command decoder. All commands are masked
when CS# is registered HIGH. CS# provides for external bank
selection on systems with multiple banks. CS# is considered part
of the command code.
Command Inputs: WE# , CAS#, and RAS# (along with CS#)
define the command being entered.
Input/Output Mask: DQM is sampled HIGH and is an input mask
signal for write accesses and an output enable signal for read
accesses. Input data is masked during a WRITE cycle. The output
buffers are placed in a High-Z state (two-clock latency) during a
READ cycle. DQM0 corresponds to DQ0–DQ7, DQM1 corresponds
to DQ8-DQ15, DQM2 corresponds to DQ16–DQ23 and DQM3
corresponds to DQ24–DQ31. DQM0–DQM3 are considered same
state when referenced as DQM.
Bank Address Input(s): BA0 and BA1 define to which bank the
ACTIVE, READ, WRITE, or PRECHARGE command is being
applied.
Address Inputs: A0–A11 are sampled during the ACTIVE com-
mand (row-address A0–A10) and READ/WRITE command
(column-address A0–A8 with A10 defining auto precharge) to
select one location out of the memory array in the respective
bank. A10 is sampled during a PRECHARGE command to
determine if all banks are to be precharged (A10 [HIGH]) or
bank selected by BA0, BA1 (LOW). The address inputs also
provide the op-code during a LOAD MODE REGISTER command.
67
CKE
Input
20
CS#
Input
17, 18, 19
WE#,
CAS#,
RAS#
DQM0–
DQM3
Input
16, 71, 28, 59
Input
22, 23
BA0, BA1 Input
25-27, 60-66, 24, 21
A0-A11
Input
2,
74,
85,
40,
4, 5, 7, 8, 10, 11, 13,
76, 77, 79, 80, 82, 83,
31, 33, 34, 36, 37, 39,
42, 45, 47, 48, 50, 51,
53, 54, 56
DQ0–
DQ31
Input/ Data I/Os: Data bus.
Output
09005aef80cd8e48
256MbSDRAMx32.p65 – Rev. B; Pub. 03/04
6
Micron Technology, Inc., reserves the right to change products or specifications without notice.
©2003 Micron Technology, Inc.
MICRON [ MICRON TECHNOLOGY ]
