256Mb: x4, x8, x16 SDRAM
Features
SDR SDRAM
MT48LC64M4A2 – 16 Meg x 4 x 4 banks
MT48LC32M8A2 – 8 Meg x 8 x 4 banks
MT48LC16M16A2 – 4 Meg x 16 x 4 banks
Features
Options
• PC100- and PC133-compliant
• Fully synchronous; all signals registered on positive
edge of system clock
• Internal, pipelined operation; column address can
be changed every clock cycle
• Internal banks for hiding row access/precharge
• Programmable burst lengths: 1, 2, 4, 8, or full page
• Auto precharge, includes concurrent auto precharge
and auto refresh modes
• Self refresh mode (not available on AT devices)
• Auto refresh
– 64ms, 8192-cycle refresh (commercial and
industrial)
– 16ms, 8192-cycle refresh (automotive)
• LVTTL-compatible inputs and outputs
• Single 3.3V ±0.3V power supply
Options
• Configurations
– 64 Meg x 4 (16 Meg x 4 x 4 banks)
– 32 Meg x 8 (8 Meg x 8 x 4 banks)
– 16 Meg x 16 (4 Meg x 16 x 4 banks)
• Write recovery (tWR)
– tWR = 2 CLK
• Plastic package – OCPL1
– 54-pin TSOP II OCPL 1 (400 mil)
(standard)
– 54-pin TSOP II OCPL 1 (400 mil)
Pb-free
•
•
Marking
•
64M4
32M8
16M16
•
Marking
– 60-ball TFBGA (x4, x8) (8mm x
16mm)
– 60-ball TFBGA (x4, x8) (8mm x
16mm) Pb-free
– 54-ball VFBGA (x16) (8mm x 14 mm)
– 54-ball VFBGA (x16) (8mm x 14 mm)
Pb-free
– 54-ball VFBGA (x16) (8mm x 8 mm)
– 54-ball VFBGA (x16) (8mm x 8 mm)
Pb-free
Timing – cycle time
– 6ns @ CL = 3 (x8, x16 only)
– 7.5ns @ CL = 3 (PC133)
– 7.5ns @ CL = 2 (PC133)
Self refresh
– Standard
– Low power
Operating temperature range
– Commercial (0˚C to +70˚C)
– Industrial (–40˚C to +85˚C)
– Automotive (–40˚C to +105˚C)
Revision
Notes:
A2
TG
1.
2.
3.
4.
FB
BB
FG2
BG2
F43
B43
-6A
-752
-7E
None
L2, 4
None
IT
AT4
:D/:G
Off-center parting line.
Only available on Revision D.
Only available on Revision G.
Contact Micron for availability.
P
Table 1: Key Timing Parameters
CL = CAS (READ) latency
Speed Grade
Clock
Frequency (MHz)
Target tRCD-tRP-CL
tRCD
(ns)
tRP
(ns)
CL (ns)
-6A
167
3-3-3
18
18
18
-75
133
3-3-3
20
20
20
-7E
133
2-2-2
15
15
15
PDF: 09005aef8091e6d1
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1
Micron Technology, Inc. reserves the right to change products or specifications without notice.
© 1999 Micron Technology, Inc. All rights reserved.
Products and specifications discussed herein are subject to change by Micron without notice.
256Mb: x4, x8, x16 SDRAM
Features
Table 2: Address Table
64 Meg x 4
32 Meg x 8
16 Meg x 16
Configuration
Parameter
16 Meg x 4 x 4 banks
8 Meg x 8 x 4 banks
4 Meg x 16 x 4 banks
Refresh count
8K
8K
8K
8K A[12:0]
8K A[12:0]
8K A[12:0]
Row addressing
Bank addressing
Column addressing
4 BA[1:0]
4 BA[1:0]
4 BA[1:0]
2K A[9:0], A11
1K A[9:0]
512 A[8:0]
Table 3: 256Mb SDR Part Numbering
Note:
Part Numbers
Architecture
Package
MT48LC64M4A2TG
64 Meg x 4
54-pin TSOP II
MT48LC64M4A2P
64 Meg x 4
54-pin TSOP II
MT48LC64M4A2FB1
64 Meg x 4
60-ball FBGA
MT48LC64M4A2BB1
64 Meg x 4
60-ball FBGA
MT48LC32M8A2TG
32 Meg x 8
54-pin TSOP II
MT48LC32M8A2P
32 Meg x 8
54-pin TSOP II
MT48LC32M8A2FB1
32 Meg x 8
60-ball FBGA
MT48LC32M8A2BB1
32 Meg x 8
60-ball FBGA
MT48LC16M16A2TG
16 Meg x 16
54-pin TSOP II
MT48LC16M16A2P
16 Meg x 16
54-pin TSOP II
MT48LC16M16A2FG
16 Meg x 16
54-ball FBGA
MT48LC16M16A2BG
16 Meg x 16
54-ball FBGA
1. FBGA Device Decoder: www.micron.com/decoder.
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Micron Technology, Inc. reserves the right to change products or specifications without notice.
© 1999 Micron Technology, Inc. All rights reserved.
256Mb: x4, x8, x16 SDRAM
Features
Contents
General Description ......................................................................................................................................... 7
Automotive Temperature .............................................................................................................................. 7
Functional Block Diagrams ............................................................................................................................... 8
Pin and Ball Assignments and Descriptions ..................................................................................................... 11
Package Dimensions ....................................................................................................................................... 15
Temperature and Thermal Impedance ............................................................................................................ 19
Electrical Specifications .................................................................................................................................. 23
Electrical Specifications – IDD Parameters ........................................................................................................ 25
Electrical Specifications – AC Operating Conditions ......................................................................................... 27
Functional Description ................................................................................................................................... 30
Commands .................................................................................................................................................... 31
COMMAND INHIBIT .................................................................................................................................. 31
NO OPERATION (NOP) ............................................................................................................................... 32
LOAD MODE REGISTER (LMR) ................................................................................................................... 32
ACTIVE ...................................................................................................................................................... 32
READ ......................................................................................................................................................... 33
WRITE ....................................................................................................................................................... 34
PRECHARGE .............................................................................................................................................. 35
BURST TERMINATE ................................................................................................................................... 35
REFRESH ................................................................................................................................................... 36
AUTO REFRESH ..................................................................................................................................... 36
SELF REFRESH ....................................................................................................................................... 36
Truth Tables ................................................................................................................................................... 37
Initialization .................................................................................................................................................. 42
Mode Register ................................................................................................................................................ 44
Burst Length .............................................................................................................................................. 46
Burst Type .................................................................................................................................................. 46
CAS Latency ............................................................................................................................................... 48
Operating Mode ......................................................................................................................................... 48
Write Burst Mode ....................................................................................................................................... 48
Bank/Row Activation ...................................................................................................................................... 49
READ Operation ............................................................................................................................................. 50
WRITE Operation ........................................................................................................................................... 59
Burst Read/Single Write .............................................................................................................................. 66
PRECHARGE Operation .................................................................................................................................. 67
Auto Precharge ........................................................................................................................................... 67
AUTO REFRESH Operation ............................................................................................................................. 79
SELF REFRESH Operation ............................................................................................................................... 81
Power-Down .................................................................................................................................................. 83
Clock Suspend ............................................................................................................................................... 84
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Micron Technology, Inc. reserves the right to change products or specifications without notice.
© 1999 Micron Technology, Inc. All rights reserved.
256Mb: x4, x8, x16 SDRAM
Features
List of Figures
Figure 1: 64 Meg x 4 Functional Block Diagram ................................................................................................. 8
Figure 2: 32 Meg x 8 Functional Block Diagram ................................................................................................. 9
Figure 3: 16 Meg x 16 Functional Block Diagram ............................................................................................. 10
Figure 4: 54-Pin TSOP (Top View) .................................................................................................................. 11
Figure 5: 60-Ball FBGA (Top View) ................................................................................................................. 12
Figure 6: 54-Ball VFBGA (Top View) ............................................................................................................... 13
Figure 7: 54-Pin Plastic TSOP "TG/P" (400 mil) ............................................................................................... 15
Figure 8: 60-Ball TFBGA "BB/FB" (8mm x 16mm) (x4, x8) ............................................................................... 16
Figure 9: 54-Ball VFBGA "BG/FG" (8mm x 14mm) (x16) .................................................................................. 17
Figure 10: 54-Ball VFBGA "B4/F4" (8mm x 8mm) (x16) ................................................................................... 18
Figure 11: Example: Temperature Test Point Location, 54-Pin TSOP (Top View) ............................................... 21
Figure 12: Example: Temperature Test Point Location, 54-Ball VFBGA (Top View) ............................................ 21
Figure 13: Example: Temperature Test Point Location, 60-Ball FBGA (Top View) .............................................. 22
Figure 14: ACTIVE Command ........................................................................................................................ 32
Figure 15: READ Command ........................................................................................................................... 33
Figure 16: WRITE Command ......................................................................................................................... 34
Figure 17: PRECHARGE Command ................................................................................................................ 35
Figure 18: Initialize and Load Mode Register .................................................................................................. 43
Figure 19: Mode Register Definition ............................................................................................................... 45
Figure 20: CAS Latency .................................................................................................................................. 48
Figure 21: Example: Meeting tRCD (MIN) When 2 < tRCD (MIN)/tCK < 3 .......................................................... 49
Figure 22: Consecutive READ Bursts .............................................................................................................. 51
Figure 23: Random READ Accesses ................................................................................................................ 52
Figure 24: READ-to-WRITE ............................................................................................................................ 53
Figure 25: READ-to-WRITE With Extra Clock Cycle ......................................................................................... 54
Figure 26: READ-to-PRECHARGE .................................................................................................................. 54
Figure 27: Terminating a READ Burst ............................................................................................................. 55
Figure 28: Alternating Bank Read Accesses ..................................................................................................... 56
Figure 29: READ Continuous Page Burst ......................................................................................................... 57
Figure 30: READ – DQM Operation ................................................................................................................ 58
Figure 31: WRITE Burst ................................................................................................................................. 59
Figure 32: WRITE-to-WRITE .......................................................................................................................... 60
Figure 33: Random WRITE Cycles .................................................................................................................. 61
Figure 34: WRITE-to-READ ............................................................................................................................ 61
Figure 35: WRITE-to-PRECHARGE ................................................................................................................. 62
Figure 36: Terminating a WRITE Burst ............................................................................................................ 63
Figure 37: Alternating Bank Write Accesses ..................................................................................................... 64
Figure 38: WRITE – Continuous Page Burst ..................................................................................................... 65
Figure 39: WRITE – DQM Operation ............................................................................................................... 66
Figure 40: READ With Auto Precharge Interrupted by a READ ......................................................................... 68
Figure 41: READ With Auto Precharge Interrupted by a WRITE ........................................................................ 69
Figure 42: READ With Auto Precharge ............................................................................................................ 70
Figure 43: READ Without Auto Precharge ....................................................................................................... 71
Figure 44: Single READ With Auto Precharge .................................................................................................. 72
Figure 45: Single READ Without Auto Precharge ............................................................................................. 73
Figure 46: WRITE With Auto Precharge Interrupted by a READ ........................................................................ 74
Figure 47: WRITE With Auto Precharge Interrupted by a WRITE ...................................................................... 74
Figure 48: WRITE With Auto Precharge ........................................................................................................... 75
Figure 49: WRITE Without Auto Precharge ..................................................................................................... 76
Figure 50: Single WRITE With Auto Precharge ................................................................................................. 77
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Micron Technology, Inc. reserves the right to change products or specifications without notice.
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256Mb: x4, x8, x16 SDRAM
Features
Figure 51:
Figure 52:
Figure 53:
Figure 54:
Figure 55:
Figure 56:
Figure 57:
Single WRITE Without Auto Precharge ............................................................................................
Auto Refresh Mode ........................................................................................................................
Self Refresh Mode ..........................................................................................................................
Power-Down Mode ........................................................................................................................
Clock Suspend During WRITE Burst ...............................................................................................
Clock Suspend During READ Burst .................................................................................................
Clock Suspend Mode .....................................................................................................................
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5
78
80
82
83
84
85
86
Micron Technology, Inc. reserves the right to change products or specifications without notice.
© 1999 Micron Technology, Inc. All rights reserved.
256Mb: x4, x8, x16 SDRAM
Features
List of Tables
Table 1: Key Timing Parameters ....................................................................................................................... 1
Table 2: Address Table ..................................................................................................................................... 2
Table 3: 256Mb SDR Part Numbering ............................................................................................................... 2
Table 4: Pin and Ball Descriptions .................................................................................................................. 14
Table 5: Temperature Limits .......................................................................................................................... 19
Table 6: Thermal Impedance Simulated Values ............................................................................................... 20
Table 7: Absolute Maximum Ratings .............................................................................................................. 23
Table 8: DC Electrical Characteristics and Operating Conditions ..................................................................... 23
Table 9: Capacitance ..................................................................................................................................... 24
Table 10: IDD Specifications and Conditions (x4, x8, x16) Revision D ................................................................ 25
Table 11: IDD Specifications and Conditions (x4, x8, x16) Revision G ................................................................ 25
Table 12: Electrical Characteristics and Recommended AC Operating Conditions ............................................ 27
Table 13: AC Functional Characteristics ......................................................................................................... 28
Table 14: Truth Table – Commands and DQM Operation ................................................................................. 31
Table 15: Truth Table – Current State Bank n, Command to Bank n .................................................................. 37
Table 16: Truth Table – Current State Bank n, Command to Bank m ................................................................. 39
Table 17: Truth Table – CKE ........................................................................................................................... 41
Table 18: Burst Definition Table ..................................................................................................................... 47
PDF: 09005aef8091e6d1
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Micron Technology, Inc. reserves the right to change products or specifications without notice.
© 1999 Micron Technology, Inc. All rights reserved.
256Mb: x4, x8, x16 SDRAM
General Description
General Description
The 256Mb SDRAM is a high-speed CMOS, dynamic random-access memory containing 268,435,456 bits. It is internally configured as a quad-bank DRAM with a synchronous interface (all signals are registered on the positive edge of the clock signal, CLK).
Each of the x4’s 67,108,864-bit banks is organized as 8192 rows by 2048 columns by 4
bits. Each of the x8’s 67,108,864-bit banks is organized as 8192 rows by 1024 columns by
8 bits. Each of the x16’s 67,108,864-bit banks is organized as 8192 rows by 512 columns
by 16 bits.
Read and write accesses to the SDRAM are burst-oriented; accesses start at a selected
location and continue for a programmed number of locations in a programmed sequence. Accesses begin with the registration of an ACTIVE command, which is then followed by a READ or WRITE command. The address bits registered coincident with the
ACTIVE command are used to select the bank and row to be accessed (BA[1:0] select the
bank; A[12:0] select the row). The address bits registered coincident with the READ or
WRITE command are used to select the starting column location for the burst access.
The SDRAM provides for programmable read or write burst lengths (BL) of 1, 2, 4, or 8
locations, or the full page, with a burst terminate option. An auto precharge function
may be enabled to provide a self-timed row precharge that is initiated at the end of the
burst sequence.
The 256Mb SDRAM uses an internal pipelined architecture to achieve high-speed operation. This architecture is compatible with the 2n rule of prefetch architectures, but it
also allows the column address to be changed on every clock cycle to achieve a highspeed, fully random access. Precharging one bank while accessing one of the other
three banks will hide the PRECHARGE cycles and provide seamless, high-speed, random-access operation.
The 256Mb SDRAM is designed to operate in 3.3V memory systems. An auto refresh
mode is provided, along with a power-saving, power-down mode. All inputs and outputs are LVTTL-compatible.
SDRAMs offer substantial advances in DRAM operating performance, including the
ability to synchronously burst data at a high data rate with automatic column-address
generation, the ability to interleave between internal banks to hide precharge time, and
the capability to randomly change column addresses on each clock cycle during a burst
access.
Automotive Temperature
The automotive temperature (AT) option adheres to the following specifications:
• 16ms refresh rate
• Self refresh not supported
• Ambient and case temperature cannot be less than –40°C or greater than +105°C
PDF: 09005aef8091e6d1
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Micron Technology, Inc. reserves the right to change products or specifications without notice.
© 1999 Micron Technology, Inc. All rights reserved.
256Mb: x4, x8, x16 SDRAM
Functional Block Diagrams
Functional Block Diagrams
Figure 1: 64 Meg x 4 Functional Block Diagram
CKE
CLK
COMMAND
DECODE
CS#
WE#
CAS#
RAS#
CONTROL
LOGIC
BANK3
BANK2
BANK1
MODE REGISTER
REFRESH 13
COUNTER
12
ROWADDRESS
MUX
13
13
BANK0
ROWADDRESS
LATCH
&
DECODER
8192
BANK0
MEMORY
ARRAY
(8192 x 2048 x 4)
1
DQM
SENSE AMPLIFIERS
4
8192
I/O GATING
DQM MASK LOGIC
READ DATA LATCH
WRITE DRIVERS
2
A[12:0]
BA[1:0]
15
ADDRESS
REGISTER
2
BANK
CONTROL
LOGIC
DATA
OUTPUT
REGISTER
4
4
2048
(x4)
1
DQ[3:0]
DATA
INPUT
REGISTER
COLUMN
DECODER
11
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COLUMNADDRESS
COUNTER/
LATCH
11
8
Micron Technology, Inc. reserves the right to change products or specifications without notice.
© 1999 Micron Technology, Inc. All rights reserved.
256Mb: x4, x8, x16 SDRAM
Functional Block Diagrams
Figure 2: 32 Meg x 8 Functional Block Diagram
CKE
CLK
COMMAND
DECODE
CS#
WE#
CAS#
RAS#
CONTROL
LOGIC
BANK3
BANK2
BANK1
MODE REGISTER
REFRESH 13
COUNTER
12
ROWADDRESS
MUX
13
13
BANK0
ROWADDRESS
LATCH
&
DECODER
8192
BANK0
MEMORY
ARRAY
(8192 x 1024 x 8)
1
DQM
SENSE AMPLIFIERS
8
8192
I/O GATING
DQM MASK LOGIC
READ DATA LATCH
WRITE DRIVERS
2
A[12:0]
BA[1:0]
15
ADDRESS
REGISTER
2
BANK
CONTROL
LOGIC
DATA
OUTPUT
REGISTER
8
8
1024
(x8)
1
DQ[7:0]
DATA
INPUT
REGISTER
COLUMN
DECODER
10
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COLUMNADDRESS
COUNTER/
LATCH
10
9
Micron Technology, Inc. reserves the right to change products or specifications without notice.
© 1999 Micron Technology, Inc. All rights reserved.
256Mb: x4, x8, x16 SDRAM
Functional Block Diagrams
Figure 3: 16 Meg x 16 Functional Block Diagram
CKE
CLK
COMMAND
DECODE
CS#
WE#
CAS#
RAS#
CONTROL
LOGIC
BANK3
BANK2
BANK1
MODE REGISTER
REFRESH 13
COUNTER
12
ROWADDRESS
MUX
13
13
BANK0
ROWADDRESS
LATCH
&
DECODER
8192
BANK0
MEMORY
ARRAY
(8192 x 512 x 16)
2
SENSE AMPLIFIERS
16
8192
I/O GATING
DQM MASK LOGIC
READ DATA LATCH
WRITE DRIVERS
2
A[12:0]
BA[1:0]
15
ADDRESS
REGISTER
2
BANK
CONTROL
LOGIC
DQML,
DQMH
DATA
OUTPUT
REGISTER
16
16
512
(x16)
2
DQ[15:0]
DATA
INPUT
REGISTER
COLUMN
DECODER
9
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COLUMNADDRESS
COUNTER/
LATCH
9
10
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© 1999 Micron Technology, Inc. All rights reserved.
256Mb: x4, x8, x16 SDRAM
Pin and Ball Assignments and Descriptions
Pin and Ball Assignments and Descriptions
Figure 4: 54-Pin TSOP (Top View)
x4
x8
NC
NC
DQ0
NC
NC
NC
DQ1
NC
NC
-
VDD
DQ0
DQ0
VDDQ
NC
DQ1
DQ1
DQ2
VSSQ
NC
DQ3
DQ2
DQ4
VDDQ
NC
DQ5
DQ3
DQ6
VSSQ
DQ7
NC
VDD
NC DQML
WE#
CAS#
RAS#
CS#
BA0
BA1
A10
A0
A1
A2
A3
VDD
-
Notes:
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x16
x16
54
53
52
51
50
49
48
47
46
45
44
43
42
41
40
39
38
37
36
35
34
33
32
31
30
29
28
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
VSS
DQ15
VSSQ
DQ14
DQ13
VDDQ
DQ12
DQ11
VSSQ
DQ10
DQ9
VDDQ
DQ8
VSS
NC
DQMH
CLK
CKE
A12
A11
A9
A8
A7
A6
A5
A4
VSS
x8
x4
DQ7
NC
DQ6
NC
DQ5
NC
DQ4
NC
DQM
-
NC
NC
DQ3
NC
NC
NC
DQ2
NC
DQM
-
1. The # symbol indicates that the signal is active LOW. A dash (-) indicates that the x8 and
x4 pin function is the same as the x16 pin function.
2. Package may or may not be assembled with a location notch.
11
Micron Technology, Inc. reserves the right to change products or specifications without notice.
© 1999 Micron Technology, Inc. All rights reserved.
256Mb: x4, x8, x16 SDRAM
Pin and Ball Assignments and Descriptions
Figure 5: 60-Ball FBGA (Top View)
64 Meg x 4 SDRAM
8mm x 16mm FB
7
8
7
8
VSS
VDD
NC
VSS
VDD
DQ0
NC
VSSQ
VDDQ
NC
VSSQ
VDDQ
NC
C
VDDQ
DQ3
C
VDDQ
DQ6
DQ1
VSSQ
D
NC
NC
D
DQ5
NC
NC
DQ2
E
VDDQ
NC
E
NC
VSSQ
VDDQ
NC
DQ2
DQ1
VSSQ
F
VDDQ
DQ4
DQ3
VSSQ
NC
NC
NC
NC
G
NC
NC
NC
NC
H
NC
VSS
VDD
NC
H
NC
VSS
VDD
NC
J
NC
DQM
WE#
CAS#
J
NC
DQM
WE#
CAS#
K
NC
CK
RAS#
NC
K
NC
CK
RAS#
NC
L
A12
CKE
NC
CS#
L
A12
CKE
NC
CS#
M
A11
A9
BA1
BA0
M
A11
A9
BA1
BA0
N
A8
A7
A0
A10
N
A8
A7
A0
A10
P
A6
A5
A2
A1
P
A6
A5
A2
A1
R
A4
VSS
VDD
A3
R
A4
VSS
VDD
A3
1
2
A
NC
B
3
4
5
6
32 Meg x 8 SDRAM
8mm x 16mm FB
1
2
A
DQ7
NC
B
DQ0
VSSQ
NC
NC
NC
VSSQ
F
VDDQ
G
Depopulated Balls
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3
4
5
6
Depopulated Balls
12
Micron Technology, Inc. reserves the right to change products or specifications without notice.
© 1999 Micron Technology, Inc. All rights reserved.
256Mb: x4, x8, x16 SDRAM
Pin and Ball Assignments and Descriptions
Figure 6: 54-Ball VFBGA (Top View)
1
2
3
A
VSS
DQ15
B
DQ14
C
5
4
6
7
8
9
VSSQ
VDDQ
DQ0
VDD
DQ13
VDDQ
VSSQ
DQ2
DQ1
DQ12
DQ11
VSSQ
VDDQ
DQ4
DQ3
D
DQ10
DQ9
VDDQ
VSSQ
DQ6
DQ5
E
DQ8
NC
VSS
VDD
LDQM
DQ7
F
UDQM
CLK
CKE
CAS#
RAS#
WE#
G
A12
A11
A9
BA0
BA1
CS#
H
A8
A7
A6
A0
A1
A10
J
VSS
A5
A4
A3
A2
VDD
Depopulated Balls
Note:
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1. The balls at A4, A5, and A6 are absent from the physical package. They are included to
illustrate that rows 4, 5, and 6 exist, but contain no solder balls.
13
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256Mb: x4, x8, x16 SDRAM
Pin and Ball Assignments and Descriptions
Table 4: Pin and Ball Descriptions
Symbol
Type
Description
CLK
Input
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.
CKE
Input
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.
CS#
Input
Chip select: CS# enables (registered LOW) and disables (registered HIGH) the command decoder. All commands are masked when CS# is registered HIGH, but READ/WRITE bursts already in
progress will continue, and DQM operation will retain its DQ mask capability while CS# is
HIGH. CS# provides for external bank selection on systems with multiple banks. CS# is considered part of the command code.
CAS#, RAS#,
WE#
Input
Command inputs: RAS#, CAS#, and WE# (along with CS#) define the command being entered.
x4, x8:
DQM
Input
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 High-Z (two-clock latency) during a READ cycle. LDQM corresponds to
DQ[7:0], and UDQM corresponds to DQ[15:8]. LDQM and UDQM are considered same-state
when referenced as DQM.
BA[1:0]
Input
Bank address input(s): BA[1:0] define to which bank the ACTIVE, READ, WRITE, or PRECHARGE
command is being applied.
A[12:0]
Input
Address inputs: A[12:0] are sampled during the ACTIVE command (row address A[12:0]) and
READ or WRITE command (column address A[9:0] and A11 for x4; A[9:0] for x8; A[8:0] for x16;
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 BA[1:0] (LOW). The address inputs also provide
the op-code during a LOAD MODE REGISTER command.
x16:
DQ[15:0]
I/O
Data input/output: Data bus for x16 (pins 4, 7, 10, 13, 42, 45, 48, and 51 are NC for x8; and
pins 2, 4, 7, 8, 10, 13, 42, 45, 47, 48, 51, and 53 are NC for x4).
x8:
DQ[7:0]
I/O
Data input/output: Data bus for x8 (pins 2, 8, 47, 53 are NC for x4).
x4:
DQ[3:0]
I/O
Data input/output: Data bus for x4.
VDDQ
Supply
DQ power: DQ power to the die for improved noise immunity.
VSSQ
Supply
DQ ground: DQ ground to the die for improved noise immunity.
VDD
Supply
Power supply: +3.3V ±0.3V.
VSS
Supply
NC
–
x16:
DQML, DQMH
LDQM, UDQM
(54-ball)
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Ground.
These should be left unconnected. For x4 and x8 parts, G1 is a no connect, but may be used as
A12 in future designs.
14
Micron Technology, Inc. reserves the right to change products or specifications without notice.
© 1999 Micron Technology, Inc. All rights reserved.
256Mb: x4, x8, x16 SDRAM
Package Dimensions
Package Dimensions
Figure 7: 54-Pin Plastic TSOP "TG/P" (400 mil)
0.10
2X 2.28
Pin #1 ID
1.2 MAX
0.375 ±0.075 TYP
2X R 0.75
22.22 ±0.08
2X R 1.00
22.42
0.80 TYP
(for reference
only)
Package may
or may not be
assembled with
a location notch.
0.71
Plated lead finish: 90% Sn, 10% Pb or 100%Sn
Plastic package material: epoxy novolac
Package width and length do not
include mold protrusion. Allowable
protrusion is 0.25 per side.
10.16 ±0.08
11.76 ±0.20
Gage plane
Package may or may not be
assembled with a location notch.
0.15
0.25
+0.10
0.10
-0.05
+0.03
-0.02
See detail A
0.50 ±0.10
0.80
Detail A
Notes:
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1. All dimensions are in millimeters.
2. Package width and length do not include mold protrusion; allowable mold protrusion is
0.25mm per side.
3. 2X means the notch is present in two locations (both ends of the device).
4. Package may or may not be assembled with a location notch.
15
Micron Technology, Inc. reserves the right to change products or specifications without notice.
© 1999 Micron Technology, Inc. All rights reserved.
256Mb: x4, x8, x16 SDRAM
Package Dimensions
Figure 8: 60-Ball TFBGA "BB/FB" (8mm x 16mm) (x4, x8)
Seating
plane
A
60X Ø0.45
Dimensions apply
to solder balls
post-reflow on Ø0.33
NSMD ball pads.
0.12 A
Ball A1 ID
8 7
Ball A1 ID
2 1
A
B
C
D
E
F
G
H
J
K
L
M
N
P
R
16 ±0.1
11.2 CTR
0.8 TYP
1.1 ±0.1
0.8 TYP
0.25 MIN
5.6 CTR
8 ±0.1
Notes:
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1.
2.
3.
4.
All dimensions are in millimeters.
Recommended pad size for PCB is 0.33mm ±0.025mm.
Solder ball material: SAC305 (96.5% Sn, 3% Ag, 0.5% Cu) or 62% Sn, 2% Ag, 36% Pb.
Topside part-marking decoder is available at www.micron.com/decoder.
16
Micron Technology, Inc. reserves the right to change products or specifications without notice.
© 1999 Micron Technology, Inc. All rights reserved.
256Mb: x4, x8, x16 SDRAM
Package Dimensions
Figure 9: 54-Ball VFBGA "BG/FG" (8mm x 14mm) (x16)
0.65 ±0.05
SEATING PLANE
C
0.12 C
6.40
1.00 MAX
BALL A1 ID
0.80 TYP
54X Ø0.45
SOLDER BALL DIAMETER
REFERS TO POST REFLOW
CONDITION. THE PREREFLOW DIAMETER IS Ø0.42
BALL A9
BALL A1 ID
BALL A1
0.80 TYP
CL
6.40
14.00 ±0.10
3.20 ±0.05
7.00 ±0.05
3.20 ±0.05
CL
4.00 ±0.05
MOLD COMPOUND: EPOXY NOVOLAC
SUBSTRATE MATERIAL: PLASTIC LAMINATE
8.00 ±0.10
SOLDER BALL MATERIAL: 62% Sn, 36% Pb, 2% Ag OR
96.5% Sn, 3%Ag, 0.5% Cu
SOLDER MASK DEFINED BALL PADS: Ø 0.40
Notes:
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1.
2.
3.
4.
All dimensions are in millimeters.
Recommended pad size for PCB is 0.4mm ±0.065mm.
Solder ball material: SAC305 (96.5% Sn, 3% Ag, 0.5% Cu) or 62% Sn, 2% Ag, 36% Pb.
Topside part-marking decoder is available at www.micron.com/decoder.
17
Micron Technology, Inc. reserves the right to change products or specifications without notice.
© 1999 Micron Technology, Inc. All rights reserved.
256Mb: x4, x8, x16 SDRAM
Package Dimensions
Figure 10: 54-Ball VFBGA "B4/F4" (8mm x 8mm) (x16)
Seating plane
A
54X Ø0.45
Dimensions apply
to solder balls postreflow on∅Ø0.40 SMD
ball pads.
9
0.12 A
Ball A1 ID
(covered by SR)
8
7
3
2
Ball A1 ID
1
A
B
C
D
6.4 CTR
E
8 ±0.1
F
G
H
0.8 TYP
J
0.9 ±0.1
0.8 TYP
6.4 CTR
0.25 MIN
8 ±0.1
Notes:
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1.
2.
3.
4.
All dimensions are in millimeters.
Recommended pad size for PCB is 0.4mm ±0.065mm.
Solder ball material: SAC305 (96.5% Sn, 3% Ag, 0.5% Cu) or 62% Sn, 2% Ag, 36% Pb.
Topside part-marking decoder is available at www.micron.com/decoder.
18
Micron Technology, Inc. reserves the right to change products or specifications without notice.
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256Mb: x4, x8, x16 SDRAM
Temperature and Thermal Impedance
Temperature and Thermal Impedance
It is imperative that the SDRAM device’s temperature specifications, shown in Table 5
(page 19), be maintained to ensure the junction temperature is in the proper operating range to meet data sheet specifications. An important step in maintaining the proper junction temperature is using the device’s thermal impedances correctly. The thermal impedances are listed in Table 6 (page 20) for the applicable die revision and
packages being made available. These thermal impedance values vary according to the
density, package, and particular design used for each device.
Incorrectly using thermal impedances can produce significant errors. Read Micron
technical note TN-00-08, “Thermal Applications” prior to using the thermal impedances listed in Table 6 (page 20). To ensure the compatibility of current and future designs, contact Micron Applications Engineering to confirm thermal impedance values.
The SDRAM device’s safe junction temperature range can be maintained when the T C
specification is not exceeded. In applications where the device’s ambient temperature
is too high, use of forced air and/or heat sinks may be required to satisfy the case temperature specifications.
Table 5: Temperature Limits
Parameter
Operating case temperature
Junction temperature
Symbol
Min
Max
Unit
Notes
TC
0
80
°C
1, 2, 3, 4
Industrial
–40
90
Automotive
–40
105
°C
3
°C
3, 5
Commercial
0
85
Industrial
–40
95
Automotive
–40
110
0
70
Commercial
Ambient temperature
TJ
Commercial
TA
Industrial
–40
85
Automotive
–40
105
–
260
Peak reflow temperature
Notes:
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TPEAK
°C
1. MAX operating case temperature, TC, is measured in the center of the package on the
top side of the device, as shown in Figure 11 (page 21), Figure 12 (page 21), and Figure 13 (page 22).
2. Device functionality is not guaranteed if the device exceeds maximum TC during operation.
3. All temperature specifications must be satisfied.
4. The case temperature should be measured by gluing a thermocouple to the top-center
of the component. This should be done with a 1mm bead of conductive epoxy, as defined by the JEDEC EIA/JESD51 standards. Take care to ensure that the thermocouple
bead is touching the case.
5. Operating ambient temperature surrounding the package.
19
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Temperature and Thermal Impedance
Table 6: Thermal Impedance Simulated Values
Die
Revision
D
Θ JA (°C/W)
Airflow =
1m/s
Θ JA (°C/W)
Airflow =
2m/s
Θ JB (°C/W) Θ JC (°C/W)
Package
Substrate
54-pin TSOP
(TG, P)
Low Conductivity
81
63.8
57.6
45.3
High Conductivity
55
47.3
44.5
39.1
Low Conductivity
64.9
50.8
44.8
31.4
High Conductivity
51.5
41.6
38.1
31.4
Low Conductivity
67
51.2
47.8
19.7
High Conductivity
40.9
35.1
32.2
18.6
Low Conductivity
122.3
105.6
98.1
89.5
High Conductivity
101.9
93.5
88.8
87.6
Low Conductivity
96.9
81.9
81.9
69.5
High Conductivity
74.0
66.3
62.7
60.7
Low Conductivity
68.8
55.9
51.1
42.1
High Conductivity
47.9
42.0
39.9
34.9
54-ball VFBGA
(BG, FG)
60-ball FBGA
(BB, FB)
G
Θ JA (°C/W)
Airflow =
0m/s
54-pin TSOP
(TG, P)
54-ball VFBGA
(B4, F4)
60-ball FBGA
(BB, FB)
Notes:
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10.3
3.2
6.7
20.7
11.5
10.9
1. For designs expected to last beyond the die revision listed, contact Micron Applications
Engineering to confirm thermal impedance values.
2. Thermal resistance data is sampled from multiple lots, and the values should be viewed
as typical.
3. These are estimates; actual results may vary.
20
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Temperature and Thermal Impedance
Figure 11: Example: Temperature Test Point Location, 54-Pin TSOP (Top View)
22.22mm
11.11mm
Test point
10.16mm
5.08mm
Note:
1. Package may or may not be assembled with a location notch.
Figure 12: Example: Temperature Test Point Location, 54-Ball VFBGA (Top View)
8.00mm
4.00mm
Test point
14.00mm
7.00mm
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Temperature and Thermal Impedance
Figure 13: Example: Temperature Test Point Location, 60-Ball FBGA (Top View)
8.00mm
4.00mm
Test point
16.00mm
8.00mm
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Electrical Specifications
Electrical Specifications
Stresses greater than those listed may cause permanent damage to the device. This is a
stress rating only, and functional operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect
reliability.
Table 7: Absolute Maximum Ratings
Voltage/Temperature
Symbol
Min
Max
Unit
Notes
Voltage on VDD/VDDQ supply relative to VSS
VDD/VDDQ
–1
4.6
V
1
Voltage on inputs, NC, or I/O balls relative to VSS
VIN
–1
4.6
Storage temperature (plastic)
TSTG
–55
150
°C
–
–
1
W
Power dissipation
Note:
1. VDD and VDDQ must be within 300mV of each other at all times. VDDQ must not exceed
VDD.
Table 8: DC Electrical Characteristics and Operating Conditions
Notes 1–3 apply to all parameters and conditions; VDD/VDDQ = 3.3V ±0.3V
Parameter/Condition
Symbol
VDD, VDDQ
Supply voltage
Min
Max
Unit
3
3.6
V
Notes
Input high voltage: Logic 1; All inputs
VIH
2
VDD + 0.3
V
4
Input low voltage: Logic 0; All inputs
VIL
–0.3
0.8
V
4
Output high voltage: IOUT = –4mA
VOH
2.4
–
V
Output low voltage: IOUT = 4mA
VOL
–
0.4
V
IL
–5
5
μA
Output leakage current: DQ are disabled; 0V ≤ VOUT ≤
VDDQ
IOZ
–5
5
μA
Operating temperature:
Commercial
TA
0
70
˚C
Industrial
TA
–40
85
˚C
Automotive
TA
–40
105
˚C
Input leakage current: Any input 0V ≤ VIN ≤ VDD (All
other balls not under test = 0V)
Notes:
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1. All voltages referenced to VSS.
2. The minimum specifications are used only to indicate cycle time at which proper operation over the full temperature range is ensured; (0°C ≤ TA ≤ +70°C (commercial), –40°C ≤
TA ≤ +85°C (industrial), and –40°C ≤ TA ≤ +105°C (automotive)).
3. An initial pause of 100μs is required after power-up, followed by two AUTO REFRESH
commands, before proper device operation is ensured. (VDD and VDDQ must be powered
up simultaneously. VSS and VSSQ must be at same potential.) The two AUTO REFRESH
command wake-ups should be repeated any time the tREF refresh requirement is exceeded.
4. VIH overshoot: VIH,max = VDDQ + 2V for a pulse width ≤ 3ns, and the pulse width cannot
be greater than one-third of the cycle rate. VIL undershoot: VIL,min = –2V for a pulse
width ≤3ns.
23
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Electrical Specifications
Table 9: Capacitance
Note 1 applies to all parameters and conditions
Package
Parameter
TSOP package
FBGA package
Min
Max
Unit
Notes
Input capacitance: CLK
CL1
2.5
3.5
pF
2
Input capacitance: All other input-only
balls
CL2
2.5
3.8
pF
3
Input/output capacitance: DQ
CL0
4
6
pF
4
Input capacitance: CLK
CL1
1.5
3.5
pF
5
Input capacitance: All other input-only
balls
CL2
1.5
3.8
pF
6
Input/output capacitance: DQ
CL0
3
6
pF
7
Notes:
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Symbol
1. This parameter is sampled. VDD, VDDQ = 3.3V; f = 1 MHz, TA = 25°C; pin under test biased
at 1.4V.
2. PC100 specifies a maximum of 4pF.
3. PC100 specifies a maximum of 5pF.
4. PC100 specifies a maximum of 6.5pF.
5. PC133 specifies a minimum of 2.5pF.
6. PC133 specifies a minimum of 2.5pF.
7. PC133 specifies a minimum of 3.0pF.
24
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Electrical Specifications – IDD Parameters
Electrical Specifications – IDD Parameters
Table 10: IDD Specifications and Conditions (x4, x8, x16) Revision D
Notes 1–5 apply to all parameters and conditions; VDD/VDDQ = +3.3V ±0.3V
Max
Parameter/Condition
Symbol
-6A
-7E
-75
Unit
Notes
Operating current: Active mode; Burst = 2; READ or WRITE; tRC
= tRC (MIN)
IDD1
135
135
125
mA
6, 7, 8,
9
Standby current: Power-down mode; All banks idle; CKE =
LOW
IDD2
2
2
2
mA
9
Standby current: Active mode; CKE = HIGH; CS# = HIGH; All
banks active after tRCD met; No accesses in progress
IDD3
40
40
40
mA
6, 8, 9,
10
Operating current: Burst mode; Page burst; READ or WRITE;
All banks active
IDD4
135
135
135
mA
6, 7, 8,
9
6, 7, 8,
9, 10,
11
Auto refresh current: CKE = HIGH; CS# =
HIGH
Self refresh current: CKE ≤ 0.2V
tRFC
= tRFC (MIN)
IDD5
285
285
270
mA
tRFC
= 7.813μs
IDD6
3.5
3.5
3.5
mA
tRFC
= 1.953μs (AT)
IDD6
8
8
8
mA
Standard
IDD7
2.5
2.5
2.5
mA
Low power (L)
IDD7
–
1.5
1.5
mA
12
Table 11: IDD Specifications and Conditions (x4, x8, x16) Revision G
Notes 1–5 apply to all parameters and conditions; VDD/VDDQ = +3.3V ±0.3V
Max
Parameter/Condition
Symbol
-6A
-7E
Unit
Notes
tRC
IDD1
100
100
mA
6, 7, 8,
9
Standby current: Power-down mode; All banks idle; CKE = LOW
IDD2
2.5
2.5
mA
9
Standby current: Active mode; CKE = HIGH; CS# = HIGH; All banks active after tRCD met; No accesses in progress
IDD3
35
35
mA
6, 8, 9,
10
Operating current: Burst mode; Page burst; READ or WRITE; All
banks active
IDD4
100
100
mA
6, 7, 8,
9
Auto refresh current: CKE = HIGH; CS# = HIGH tRFC = tRFC (MIN)
IDD5
150
150
mA
6, 7, 8,
9, 10,
11
Operating current: Active mode; Burst = 2; READ or WRITE;
(MIN)
Self refresh current: CKE ≤ 0.2V
Notes:
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tRC
=
tRFC
= 7.813μs
IDD6
4
4
mA
tRFC
= 1.953μs (AT)
IDD6
8
8
mA
Standard
IDD7
3
3
mA
Low power (L)
IDD7
1.5
1.5
mA
12
1. All voltages referenced to VSS.
2. The minimum specifications are used only to indicate cycle time at which proper operation over the full temperature range is ensured; (0°C ≤ TA ≤ +70°C (commercial), –40°C ≤
TA ≤ +85°C (industrial), and –40°C ≤ TA ≤ +105°C (automotive)).
3. An initial pause of 100μs is required after power-up, followed by two AUTO REFRESH
commands, before proper device operation is ensured. (VDD and VDDQ must be powered
up simultaneously. VSS and VSSQ must be at same potential.) The two AUTO REFRESH
25
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Electrical Specifications – IDD Parameters
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
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command wake-ups should be repeated any time the tREF refresh requirement is exceeded.
AC operating and IDD test conditions have VIL = 0V and VIH = 3.0V using a measurement
reference level of 1.5V. If the input transition time is longer than 1ns, then the timing is
measured from VIL, max and VIH,min and no longer from the 1.5V midpoint. CLK should
always be 1.5V referenced to crossover. Refer to Micron technical note TN-48-09.
IDD specifications are tested after the device is properly initialized.
IDD is dependent on output loading and cycle rates. Specified values are obtained with
minimum cycle time and the outputs open.
The IDD current will increase or decrease proportionally according to the amount of frequency alteration for the test condition.
Address transitions average one transition every two clocks.
For -75, CL = 3 and tCK = 7.5ns; for -7E, CL = 2 and tCK = 7.5ns.
Other input signals are allowed to transition no more than once every two clocks and
are otherwise at valid VIH or VIL levels.
CKE is HIGH during REFRESH command period tRFC (MIN) else CKE is LOW. The IDD6 limit
is actually a nominal value and does not result in a fail value.
Enables on-chip refresh and address counters.
PC100 specifies a maximum of 4pF.
PC100 specifies a maximum of 5pF.
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Electrical Specifications – AC Operating Conditions
Electrical Specifications – AC Operating Conditions
Table 12: Electrical Characteristics and Recommended AC Operating Conditions
Notes 1–5 apply to all parameters and conditions
-6A
Parameter
Access time from CLK
(positive edge)
-7E
-75
Symbol
Min
Max
Min
Max
Min
Max
CL = 3
tAC(3)
–
5.4
–
5.4
–
5.4
Unit Notes
ns
7
CL = 2
tAC(2)
–
7.56
–
5.4
–
6
ns
7
CL = 1
tAC(1)
–
176
–
–
–
–
ns
7
Address hold time
tAH
0.8
–
0.8
–
0.8
–
ns
Address setup time
tAS
1.5
–
1.5
–
1.5
–
ns
CLK high-level width
tCH
2.5
–
2.5
–
2.5
–
ns
CLK low-level width
tCL
2.5
–
2.5
–
ns
2.5
–
CL = 3
tCK(3)
6
–
7
–
7.5
–
ns
8
CL = 2
tCK(2)
106
–
7.5
–
10
–
ns
8
CL = 1
tCK(1)
206
–
–
–
–
–
ns
8
CKE hold time
tCKH
0.8
–
0.8
–
0.8
–
ns
CKE setup time
tCKS
1.5
–
1.5
–
1.5
–
ns
CS#, RAS#, CAS#, WE#, DQM hold time
tCMH
0.8
–
0.8
–
0.8
–
ns
CS#, RAS#, CAS#, WE#, DQM setup time
tCMS
1.5
–
1.5
–
1.5
–
ns
Data-in hold time
tDH
0.8
–
0.8
–
0.8
–
ns
Data-in setup time
tDS
1.5
–
1.5
–
1.5
–
ns
CL = 3
tHZ(3)
–
5.4
–
5.4
–
5.4
ns
9
CL = 2
tHZ(2)
–
7.56
–
5.4
–
6
ns
9
CL = 1
tHZ(1)
–
176
–
–
–
–
ns
9
Clock cycle time
Data-out High-Z time
Data-out Low-Z time
tLZ
1
–
1
–
1
–
ns
Data-out hold time (load)
tOH
3
–
3
–
3
–
ns
Data-out hold time (no load)
tOHn
1.8
–
1.8
–
1.8
–
ns
ACTIVE-to-PRECHARGE command
tRAS
42
120,000
37
120,000
44
120,000
ns
tRC
60
–
60
–
66
–
ns
ACTIVE-to-READ or WRITE delay
tRCD
18
–
15
–
20
–
ns
Refresh period (8192 rows)
tREF
–
64
–
64
–
64
ms
–
16
–
16
–
16
ms
ACTIVE-to-ACTIVE command period
Refresh period – automotive (8192 rows)
AUTO REFRESH period
PRECHARGE command period
ACTIVE bank a to ACTIVE bank b command
Transition time
WRITE recovery time
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tREF
AT
10
11
tRFC
60
–
66
–
66
–
ns
tRP
18
–
15
–
20
–
ns
tRRD
12
–
14
–
15
–
ns
tT
0.3
1.2
0.3
1.2
0.3
1.2
ns
12
tWR
1 CLK +
6ns
–
1 CLK +
7ns
–
1 CLK +
7.5ns
–
ns
13
12
–
14
–
15
–
ns
14
27
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Electrical Specifications – AC Operating Conditions
Table 12: Electrical Characteristics and Recommended AC Operating Conditions (Continued)
Notes 1–5 apply to all parameters and conditions
-6A
Parameter
-7E
-75
Symbol
Min
Max
Min
Max
Min
Max
tXSR
67
–
67
–
75
–
Symbol
-6A
Exit SELF REFRESH-to-ACTIVE command
Unit Notes
ns
15
Table 13: AC Functional Characteristics
Notes 2–5 apply to all parameters and conditions
Parameter
Last data-in to burst STOP command
tBDL
1
READ/WRITE command to READ/WRITE command
tCCD
1
Last data-in to new READ/WRITE command
tCDL
tCKED
CKE to clock disable or power-down entry mode
1
1
-7E
-75
Unit
Notes
1
1
tCK
16
1
1
tCK
16
1
tCK
16
1
tCK
17
18, 19
1
1
Data-in to ACTIVE command
tDAL
5
4
5
tCK
Data-in to PRECHARGE command
tDPL
2
2
2
tCK
19, 20
DQM to input data delay
tDQD
0
0
0
tCK
16
DQM to data mask during WRITEs
tDQM
0
tCK
16
DQM to data High-Z during READs
tDQZ
2
2
2
tCK
16
WRITE command to input data delay
tDWD
0
0
0
tCK
16
LOAD MODE REGISTER command to ACTIVE or REFRESH command
tMRD
2
tCK
21
CKE to clock enable or power-down exit setup mode
tPED
1
tCK
17
Last data-in to PRECHARGE command
tRDL
2
2
2
tCK
19, 20
CL = 3
tROH(3)
3
3
3
tCK
16
CL = 2
tROH(2)
2
tCK
16
CL = 1
tROH(1)
–
tCK
16
Data-out High-Z from PRECHARGE command
Notes:
0
2
1
2
1
0
2
1
2
–
1. Minimum specifications are used only to indicate the cycle time at which proper operation over the full temperature range is ensured:
0˚C ≤ TA ≤ +70˚C (commercial)
-40˚C ≤ TA ≤ +85˚C (industrial)
-40˚C ≤ TA ≤ +105˚C (automotive)
2. An initial pause of 100μs is required after power-up, followed by two AUTO REFRESH
commands, before proper device operation is ensured. (VDD and VDDQ must be powered
up simultaneously. VSS and VSSQ must be at same potential.) The two AUTO REFRESH
command wake-ups should be repeated any time the tREF refresh requirement is exceeded.
3. In addition to meeting the transition rate specification, the clock and CKE must transit
between VIH and VIL (or between VIL and VIH) in a monotonic manner.
4. Outputs measured at 1.5V with equivalent load:
Q
50pF
5. AC operating and IDD test conditions have VIL = 0V and VIH = 3.0V using a measurement
reference level of 1.5V. If the input transition time is longer than 1ns, then the timing is
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Electrical Specifications – AC Operating Conditions
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
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measured from VIL,max and VIH,min and no longer from the 1.5V midpoint. CLK should always be 1.5V referenced to crossover. Refer to Micron technical note TN-48-09.
Not applicable for Revision D.
tAC for -75/-7E at CL = 3 with no load is 4.6ns and is guaranteed by design.
The clock frequency must remain constant (stable clock is defined as a signal cycling
within timing constraints specified for the clock pin) during access or precharge states
(READ, WRITE, including tWR, and PRECHARGE commands). CKE may be used to reduce
the data rate.
tHZ defines the time at which the output achieves the open circuit condition; it is not a
reference to VOH or VOL. The last valid data element will meet tOH before going High-Z.
Parameter guaranteed by design.
DRAM devices should be evenly addressed when being accessed. Disproportionate accesses to a particular row address may result in reduction of the product lifetime.
AC characteristics assume tT = 1ns.
Auto precharge mode only. The precharge timing budget (tRP) begins at 6ns for -6A, 7ns
for -7E, and 7.5ns for -75 after the first clock delay, after the last WRITE is executed.
Precharge mode only.
CLK must be toggled a minimum of two times during this period.
Required clocks are specified by JEDEC functionality and are not dependent on any timing parameter.
Timing is specified by tCKS. Clock(s) specified as a reference only at minimum cycle rate.
Timing is specified by tWR plus tRP. Clock(s) specified as a reference only at minimum cycle rate.
Based on tCK = 7.5ns for -75 and -7E, 6ns for -6A.
Timing is specified by tWR.
JEDEC and PC100 specify three clocks.
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256Mb: x4, x8, x16 SDRAM
Functional Description
Functional Description
In general, 256Mb SDRAM devices (16 Meg x 4 x 4 banks, 8 Meg x 8 x 4 banks, and 4 Meg
x 16 x 4 banks) are quad-bank DRAM that operate at 3.3V and include a synchronous
interface. All signals are registered on the positive edge of the clock signal, CLK. Each of
the x4’s 67,108,864-bit banks is organized as 8192 rows by 2048 columns by 4 bits. Each
of the x8’s 67,108,864-bit banks is organized as 8192 rows by 1024 columns by 8 bits.
Each of the x16’s 67,108,864-bit banks is organized as 8192 rows by 512 columns by 16
bits.
Read and write accesses to the SDRAM are burst-oriented; accesses start at a selected
location and continue for a programmed number of locations in a programmed sequence. Accesses begin with the registration of an ACTIVE command, followed by a
READ or WRITE command. The address bits registered coincident with the ACTIVE
command are used to select the bank and row to be accessed (BA0 and BA1 select the
bank, A[12:0] select the row). The address bits (x4: A[9:0], A11; x8: A[9:0]; x16: A[8:0]) registered coincident with the READ or WRITE command are used to select the starting
column location for the burst access.
Prior to normal operation, the SDRAM must be initialized. The following sections provide detailed information covering device initialization, register definition, command
descriptions, and device operation.
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Commands
Commands
The following table provides a quick reference of available commands, followed by a
written description of each command. Additional Truth Tables (Table 15 (page 37), Table 16 (page 39), and Table 17 (page 41)) provide current state/next state information.
Table 14: Truth Table – Commands and DQM Operation
Note 1 applies to all parameters and conditions
Name (Function)
CS# RAS# CAS# WE# DQM
ADDR
DQ
Notes
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)
L
L
H
H
X
Bank/row
X
2
READ (select bank and column, and start READ burst)
L
H
L
H
L/H
Bank/col
X
3
WRITE (select bank and column, and start WRITE burst)
L
H
L
L
L/H
Bank/col
Valid
3
BURST TERMINATE
L
H
H
L
X
X
Active
4
PRECHARGE (Deactivate row in bank or banks)
L
L
H
L
X
Code
X
5
AUTO REFRESH or SELF REFRESH (enter self refresh mode)
L
L
L
H
X
X
X
6, 7
LOAD MODE REGISTER
L
L
L
L
X
Op-code
X
8
Write enable/output enable
X
X
X
X
L
X
Active
9
Write inhibit/output High-Z
X
X
X
X
H
X
High-Z
9
Notes:
1. CKE is HIGH for all commands shown except SELF REFRESH.
2. A[0:n] provide row address (where An is the most significant address bit), BA0 and BA1
determine which bank is made active.
3. A[0:i] provide column address (where i = the most significant column address for a given
device configuration). A10 HIGH enables the auto precharge feature (nonpersistent),
while A10 LOW disables the auto precharge feature. BA0 and BA1 determine which
bank is being read from or written to.
4. The purpose of the BURST TERMINATE command is to stop a data burst, thus the command could coincide with data on the bus. However, the DQ column reads a “Don’t
Care” state to illustrate that the BURST TERMINATE command can occur when there is
no data present.
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. A[11:0] define the op-code written to the mode register.
9. Activates or deactivates the DQ during WRITEs (zero-clock delay) and READs (two-clock
delay).
COMMAND INHIBIT
The COMMAND INHIBIT function prevents new commands from being executed by
the device, regardless of whether the CLK signal is enabled. The device is effectively deselected. Operations already in progress are not affected.
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Commands
NO OPERATION (NOP)
The NO OPERATION (NOP) command is used to perform a NOP to the selected device
(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 (LMR)
The mode registers are loaded via inputs A[n:0] (where An is the most significant address term), BA0, and BA1(see Mode Register (page 44)). 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.
ACTIVE
The ACTIVE command is used to activate a row in a particular bank for a subsequent
access. The value on the BA0, BA1 inputs selects the bank, and the address provided selects the row. This row remains active 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.
Figure 14: ACTIVE Command
CLK
CKE
HIGH
CS#
RAS#
CAS#
WE#
Address
Row address
BA0, BA1
Bank address
Don’t Care
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Commands
READ
The READ command is used to initiate a burst read access to an active row. The values
on the BA0 and BA1 inputs select the bank; the address provided selects the starting column location. The value on input A10 determines whether auto precharge is used. If auto precharge is selected, the row being accessed is precharged at the end of the READ
burst; if auto precharge is not selected, the row remains open for subsequent accesses.
Read data appears on the DQ subject to the logic level on the DQM inputs two clocks
earlier. If a given DQM signal was registered HIGH, the corresponding DQ will be HighZ two clocks later; if the DQM signal was registered LOW, the DQ will provide valid data.
Figure 15: READ Command
CLK
CKE
HIGH
CS#
RAS#
CAS#
WE#
Address
Column address
EN AP
A101
DIS AP
BA0, BA1
Bank address
Don’t Care
Note:
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1. EN AP = enable auto precharge, DIS AP = disable auto precharge.
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Commands
WRITE
The WRITE command is used to initiate a burst write access to an active row. The values
on the BA0 and BA1 inputs select the bank; the address provided selects the starting column location. The value on input A10 determines whether auto precharge is used. If auto precharge is selected, the row being accessed is precharged at the end of the write
burst; if auto precharge is not selected, the row remains open for subsequent accesses.
Input data appearing on the DQ is written to the memory array, subject to the DQM input logic level appearing coincident with the data. If a given DQM signal is registered
LOW, the corresponding data is written to memory; if the DQM signal is registered
HIGH, the corresponding data inputs are ignored and a WRITE is not executed to that
byte/column location.
Figure 16: WRITE Command
CLK
CKE
HIGH
CS#
RAS#
CAS#
WE#
Address
Column address
EN AP
A101
DIS AP
BA0, BA1
Bank address
Valid address
Note:
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Don’t Care
1. EN AP = enable auto precharge, DIS AP = disable auto precharge.
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Commands
PRECHARGE
The PRECHARGE command is used to deactivate the open row in a particular bank or
the open row in all banks. The bank(s) will be available for a subsequent row access a
specified time (tRP) after the PRECHARGE command is issued. Input A10 determines
whether one or all banks are to be precharged, and in the case where only one bank is
precharged, inputs BA0 and BA1 select the bank. Otherwise BA0 and BA1 are treated as
“Don’t Care.” After a bank has been precharged, it is in the idle state and must be activated prior to any READ or WRITE commands are issued to that bank.
Figure 17: PRECHARGE Command
CLK
CKE
HIGH
CS#
RAS#
CAS#
WE#
Address
All banks
A10
Bank selected
BA0, BA1
Bank address
Valid address
Don’t Care
BURST TERMINATE
The BURST TERMINATE command is used to truncate either fixed-length or continuous page bursts. The most recently registered READ or WRITE command prior to the
BURST TERMINATE command is truncated.
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Commands
REFRESH
AUTO REFRESH
AUTO REFRESH is used during normal operation of the SDRAM and is analogous to
CAS#-BEFORE-RAS# (CBR) refresh in conventional DRAMs. This command is nonpersistent, so it must be issued each time a refresh is required. All active banks must be precharged prior to issuing an AUTO REFRESH command. The AUTO REFRESH command
should not be issued until the minimum tRP has been met after the PRECHARGE command, as shown in Bank/Row Activation (page 49).
The addressing is generated by the internal refresh controller. This makes the address
bits a “Don’t Care” during an AUTO REFRESH command. Regardless of device width,
the 256Mb SDRAM requires 8192 AUTO REFRESH cycles every 64ms (commercial and
industrial) or 16ms (automotive). Providing a distributed AUTO REFRESH command
every 7.813μs (commercial and industrial) or 1.953μs (automotive) will meet the refresh
requirement and ensure that each row is refreshed. Alternatively, 8192 AUTO REFRESH
commands can be issued in a burst at the minimum cycle rate (tRFC), once every 64ms
(commercial and industrial) or 16ms (automotive).
SELF REFRESH
The SELF REFRESH command can be used to retain data in the SDRAM, even if the rest
of the system is powered-down. When in the self refresh mode, the SDRAM retains data
without external clocking.
The SELF REFRESH command is initiated like an AUTO REFRESH command except
CKE is disabled (LOW). After the SELF REFRESH command is registered, all the inputs
to the SDRAM become a “Don’t Care” with the exception of CKE, which must remain
LOW.
After self refresh mode is engaged, the SDRAM provides its own internal clocking, causing it to perform its own AUTO REFRESH cycles. The SDRAM must remain in self refresh mode for a minimum period equal to tRAS and may remain in self refresh mode
for an indefinite period beyond that.
The procedure for exiting self refresh requires a sequence of commands. First, CLK
must be stable (stable clock is defined as a signal cycling within timing constraints
specified for the clock pin) prior to CKE going back HIGH. After CKE is HIGH, the
SDRAM must have NOP commands issued (a minimum of two clocks) for tXSR because
time is required for the completion of any internal refresh in progress.
Upon exiting the self refresh mode, AUTO REFRESH commands must be issued at the
specified intervals, as both SELF REFRESH and AUTO REFRESH utilize the row refresh
counter.
Self refresh is not supported on automotive temperature devices.
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Truth Tables
Truth Tables
Table 15: Truth Table – Current State Bank n, Command to Bank n
Notes 1–6 apply to all parameters and conditions
Current State
CS# RAS# CAS#
Any
Idle
Row active
Read
(auto precharge disabled)
Write
(auto precharge disabled)
Notes:
WE# Command/Action
Notes
H
X
X
X
COMMAND INHIBIT (NOP/continue previous operation)
L
H
H
H
NO OPERATION (NOP/continue previous operation)
L
L
H
H
ACTIVE (select and activate row)
L
L
L
H
AUTO REFRESH
L
L
L
L
LOAD MODE REGISTER
7
L
L
H
L
PRECHARGE
8
L
H
L
H
READ (select column and start READ burst)
9
L
H
L
L
WRITE (select column and start WRITE burst)
9
L
L
H
L
PRECHARGE (deactivate row in bank or banks)
10
L
H
L
H
READ (select column and start new READ burst)
9
L
H
L
L
WRITE (select column and start WRITE burst)
9
L
L
H
L
PRECHARGE (truncate READ burst, start PRECHARGE)
10
L
H
H
L
BURST TERMINATE
11
L
H
L
H
READ (select column and start READ burst)
9
L
H
L
L
WRITE (select column and start new WRITE burst)
9
L
L
H
L
PRECHARGE (truncate WRITE burst, start PRECHARGE)
10
L
H
H
L
BURST TERMINATE
11
7
1. This table applies when CKEn-1 was HIGH and CKEn is HIGH (see Table 17 (page 41))
and after tXSR has been met (if the previous state was self refresh).
2. This table is bank-specific, except where noted (for example, the current state is for a
specific bank and the commands shown can be issued to that bank when in that state).
Exceptions are covered 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.
4. The following states must not be interrupted by a command issued to the same bank.
COMMAND INHIBIT or NOP commands, or supported commands to the other bank
should be issued on any clock edge occurring during these states. Supported commands
to any other bank are determined by the bank’s current state and the conditions described in this and the following table.
Precharging: Starts with registration of a PRECHARGE command and ends when tRP is
met. After tRP is met, the bank will be in the idle state.
Row activating: Starts with registration of an ACTIVE command and ends when tRCD is
met. After tRCD is met, the bank will be in the row active state.
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Truth Tables
Read with auto precharge enabled: Starts with registration of a READ command
with auto precharge enabled and ends when tRP has been met. After tRP is met, the
bank will be in the idle state.
Write with auto precharge enabled: Starts with registration of a WRITE command
with auto precharge enabled and ends when tRP has been met. After tRP is met, the
bank will be in the idle state.
5. The following states must not be interrupted by any executable command; COMMAND
INHIBIT or NOP commands must be applied on each positive clock edge during these
states.
Refreshing: Starts with registration of an AUTO REFRESH command and ends when
tRFC is met. After tRFC is met, the device will be in the all banks idle state.
Accessing mode register: Starts with registration of a LOAD MODE REGISTER command and ends when tMRD has been met. After tMRD is met, the device will be in the
all banks idle state.
6.
7.
8.
9.
10.
11.
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Precharging all: Starts with registration of a PRECHARGE ALL command and ends
when tRP is met. After tRP is met, all banks will be in the idle state.
All states and sequences not shown are illegal or reserved.
Not bank specific; requires that all banks are idle.
Does not affect the state of the bank and acts as a NOP to that bank.
READs or WRITEs listed in the Command/Action column include READs or WRITEs with
auto precharge enabled and READs or WRITEs with auto precharge disabled.
May or may not be bank specific; if all banks need to be precharged, each must be in a
valid state for precharging.
Not bank-specific; BURST TERMINATE affects the most recent READ or WRITE burst, regardless of bank.
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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#
Any
WE# Command/Action
Notes
H
X
X
X
COMMAND INHIBIT (NOP/continue previous operation)
L
H
H
H
NO OPERATION (NOP/continue previous operation)
Idle
X
X
X
X
Any command otherwise supported for bank m
Row activating, active, or
precharging
L
L
H
H
ACTIVE (select and activate row)
L
H
L
H
READ (select column and start READ burst)
7
L
H
L
L
WRITE (select column and start WRITE burst)
7
L
L
H
L
PRECHARGE
L
L
H
H
ACTIVE (select and activate row)
L
H
L
H
READ (select column and start new READ burst)
7, 10
L
H
L
L
WRITE (select column and start WRITE burst)
7, 11
L
L
H
L
PRECHARGE
L
L
H
H
ACTIVE (select and activate row)
L
H
L
H
READ (select column and start READ burst)
7, 12
L
H
L
L
WRITE (select column and start new WRITE burst)
7, 13
L
L
H
L
PRECHARGE
L
L
H
H
ACTIVE (select and activate row)
L
H
L
H
READ (select column and start new READ burst)
7, 8, 14
L
H
L
L
WRITE (select column and start WRITE burst)
7, 8, 15
L
L
H
L
PRECHARGE
L
L
H
H
ACTIVE (select and activate row)
L
H
L
H
READ (select column and start READ burst)
7, 8, 16
L
H
L
L
WRITE (select column and start new WRITE burst)
7, 8, 17
L
L
H
L
PRECHARGE
Read
(auto precharge disabled)
Write
(auto precharge disabled)
Read
(with auto precharge)
Write
(with auto precharge)
Notes:
9
9
9
9
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).
2. This table describes alternate bank operation, except where noted; for example, the current 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 covered 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.
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Truth Tables
Read with auto precharge enabled: Starts with registration of a READ command
with auto precharge enabled and ends when tRP has been met. After tRP is met, the
bank will be in the idle state.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
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Write with auto precharge enabled: Starts with registration of a WRITE command
with auto precharge enabled and ends when tRP has been met. After tRP is met, the
bank will be in the idle state.
AUTO REFRESH, SELF REFRESH, and LOAD MODE REGISTER commands can only be issued when all banks are idle.
A BURST TERMINATE command cannot be issued to another bank; it applies to the bank
represented by the current state only.
All states and sequences not shown are illegal or reserved.
READs or WRITEs to bank m listed in the Command/Action column include READs or
WRITEs with auto precharge enabled and READs or WRITEs with auto precharge disabled.
Concurrent auto precharge: Bank n will initiate the auto precharge command when its
burst has been interrupted by bank m burst.
The burst in bank n continues as initiated.
For a READ without auto precharge interrupted by a READ (with or without auto precharge), the READ to bank m will interrupt the READ on bank n, CAS latency (CL) later.
For a READ without auto precharge interrupted by a WRITE (with or without auto precharge), the WRITE to bank m will interrupt the READ on bank n when registered. DQM
should be used one clock prior to the WRITE command to prevent bus contention.
For a WRITE without auto precharge interrupted by a READ (with or without auto precharge), the READ to bank m will interrupt the WRITE on bank n when registered, with
the data-out appearing CL later. The last valid WRITE to bank n will be data-in registered one clock prior to the READ to bank m.
For a WRITE without auto precharge interrupted by a WRITE (with or without auto precharge), the WRITE to bank m will interrupt the WRITE on bank n when registered. The
last valid WRITE to bank n will be data-in registered one clock prior to the READ to bank
m.
For a READ with auto precharge interrupted by a READ (with or without auto precharge), the READ to bank m will interrupt the READ on bank n, CL later. The PRECHARGE to bank n will begin when the READ to bank m is registered.
For a READ with auto precharge interrupted by a WRITE (with or without auto precharge), the WRITE to bank m will interrupt the READ on bank n when registered. DQM
should be used two clocks prior to the WRITE command to prevent bus contention. The
PRECHARGE to bank n will begin when the WRITE to bank m is registered.
For a WRITE with auto precharge interrupted by a READ (with or without auto precharge), the READ to bank m will interrupt the WRITE on bank n when registered, with
the data-out appearing CL later. The PRECHARGE to bank n will begin after tWR is met,
where tWR begins when the READ to bank m is registered. The last valid WRITE bank n
will be data-in registered one clock prior to the READ to bank m.
For a WRITE with auto precharge interrupted by a WRITE (with or without auto precharge), the WRITE to bank m will interrupt the WRITE on bank n when registered. The
PRECHARGE to bank n will begin after tWR is met, where tWR begins when the WRITE
to bank m is registered. The last valid WRITE to bank n will be data registered one clock
to the WRITE to bank m.
40
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Truth Tables
Table 17: Truth Table – CKE
Notes 1–4 apply to all parameters and conditions
Current State
CKEn-1
CKEn
Power-down
L
Commandn
Actionn
X
Maintain power-down
X
Maintain self refresh
L
Self refresh
Clock suspend
Power-down
L
H
Self refresh
X
Maintain clock suspend
COMMAND INHIBIT or NOP
Exit power-down
5
COMMAND INHIBIT or NOP
Exit self refresh
6
X
Exit clock suspend
7
COMMAND INHIBIT or NOP
Power-down entry
AUTO REFRESH
Self refresh entry
VALID
Clock suspend entry
Clock suspend
All banks idle
H
L
All banks idle
Reading or writing
H
Notes:
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H
Notes
See Table 16 (page 39).
1. CKEn is the logic state of CKE at clock edge n; CKEn-1 was the state of CKE at the previous clock edge.
2. Current state is the state of the SDRAM immediately prior to clock edge n.
3. COMMANDn is the command registered at clock edge n, and ACTIONn is a result of
COMMANDn.
4. All states and sequences not shown are illegal or reserved.
5. Exiting power-down at clock edge n will put the device in the all banks idle state in time
for clock edge n + 1 (provided that tCKS is met).
6. Exiting self refresh at clock edge n will put the device in the all banks idle state after
tXSR is met. COMMAND INHIBIT or NOP commands should be issued on any clock edges
occurring during the tXSR period. A minimum of two NOP commands must be provided
during the tXSR period.
7. After exiting clock suspend at clock edge n, the device will resume operation and recognize the next command at clock edge n + 1.
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Initialization
Initialization
SDRAM must be powered up and initialized in a predefined manner. Operational procedures other than those specified may result in undefined operation. After power is applied to V DD and V DDQ (simultaneously) and the clock is stable (stable clock is defined
as a signal cycling within timing constraints specified for the clock pin), the SDRAM requires a 100μs delay prior to issuing any command other than a COMMAND INHIBIT or
NOP. Starting at some point during this 100μs period and continuing at least through
the end of this period, COMMAND INHIBIT or NOP commands must be applied.
After the 100μs delay has been satisfied with at least one COMMAND INHIBIT or NOP
command having been applied, a PRECHARGE command should be applied. All banks
must then be precharged, thereby placing the device in the all banks idle state.
Once in the idle state, at least two AUTO REFRESH cycles must be performed. After the
AUTO REFRESH cycles are complete, the SDRAM is ready for mode register programming. Because the mode register will power up in an unknown state, it must be loaded
prior to applying any operational command. If desired, the two AUTO REFRESH commands can be issued after the LMR command.
The recommended power-up sequence for SDRAM:
1. Simultaneously apply power to V DD and V DDQ.
2. Assert and hold CKE at a LVTTL logic LOW since all inputs and outputs are LVTTLcompatible.
3. Provide stable CLOCK signal. Stable clock is defined as a signal cycling within timing constraints specified for the clock pin.
4. Wait at least 100μs prior to issuing any command other than a COMMAND INHIBIT or NOP.
5. Starting at some point during this 100μs period, bring CKE HIGH. Continuing at
least through the end of this period, 1 or more COMMAND INHIBIT or NOP commands must be applied.
6. Perform a PRECHARGE ALL command.
7. Wait at least tRP time; during this time NOPs or DESELECT commands must be
given. All banks will complete their precharge, thereby placing the device in the all
banks idle state.
8. Issue an AUTO REFRESH command.
9. Wait at least tRFC time, during which only NOPs or COMMAND INHIBIT commands are allowed.
10. Issue an AUTO REFRESH command.
11. Wait at least tRFC time, during which only NOPs or COMMAND INHIBIT commands are allowed.
12. The SDRAM is now ready for mode register programming. Because the mode register will power up in an unknown state, it should be loaded with desired bit values
prior to applying any operational command. Using the LMR command, program
the mode register. The mode register is programmed via the MODE REGISTER SET
command with BA1 = 0, BA0 = 0 and retains the stored information until it is programmed again or the device loses power. Not programming the mode register
upon initialization will result in default settings which may not be desired. Outputs are guaranteed High-Z after the LMR command is issued. Outputs should be
High-Z already before the LMR command is issued.
13. Wait at least tMRD time, during which only NOP or DESELECT commands are allowed.
At this point the DRAM is ready for any valid command.
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Initialization
Note:
More than two AUTO REFRESH commands can be issued in the sequence. After steps 9
and 10 are complete, repeat them until the desired number of AUTO REFRESH + tRFC
loops is achieved.
Figure 18: Initialize and Load Mode Register
T0
CK
T1
((
))
((
))
tCK
((
))
tCKS tCKH
Tn + 1
tCH
((
))
((
))
To + 1
tCL
((
))
((
))
((
))
((
))
((
))
Tp + 1
Tp + 2
Tp + 3
((
))
CKE
((
))
((
))
COMMAND
((
))
((
))
DQM/DQML,
DQMU
((
))
((
))
((
))
((
))
((
))
((
))
((
))
((
))
A[9:0],
A[12:11]
((
))
((
))
((
))
((
))
((
))
((
))
((
))
((
))
A10
((
))
((
))
((
))
((
))
((
))
((
))
((
))
((
))
((
))
((
))
((
))
((
))
((
))
((
))
tRFC
tRFC
tCMS tCMH
BA[1:0]
DQ
NOP2
PRECHARGE
ALL BANKS
SINGLE BANK
((
))
((
))
((
))
T = 100μs
MIN
ALL
BANKS
High-Z
((
))
((
))
AUTO
REFRESH
((
))
NOP2
((
))
AUTO
REFRESH
((
))
NOP2
((
))
LOAD MODE
REGISTER
tAS
NOP2
ACTIVE
tAH5
ROW
CODE
tAS
tAH
ROW
CODE
Bank
Address
((
))
tRP
Power-up:
VDD and
CLK stable
Precharge
all banks
AUTO REFRESH
AUTO REFRESH
tMRD
Program Mode Register1,3,4
DON’T CARE
UNDEFINED
Notes:
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1.
2.
3.
4.
5.
The mode register may be loaded prior to the AUTO REFRESH cycles if desired.
If CS is HIGH at clock HIGH time, all commands applied are NOP.
JEDEC and PC100 specify three clocks.
Outputs are guaranteed High-Z after command is issued.
A12 should be a LOW at tP + 1.
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Mode Register
Mode Register
The mode register defines the specific mode of operation, including burst length (BL),
burst type, CAS latency (CL), operating mode, and write burst mode. The mode register
is programmed via the LOAD MODE REGISTER command and retains the stored information until it is programmed again or the device loses power.
Mode register bits M[2:0] specify the BL; M3 specifies the type of burst; M[6:4] specify
the CL; M7 and M8 specify the operating mode; M9 specifies the write burst mode; and
M10–Mn should be set to zero to ensure compatibility with future revisions. Mn + 1 and
Mn + 2 should be set to zero to select the mode register.
The mode registers must be loaded when all banks are idle, and the controller must wait
tMRD before initiating the subsequent operation. Violating either of these requirements
will result in unspecified operation.
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Mode Register
Figure 19: Mode Register Definition
A12 A11 A10
12
11
10
A9
8
9
WB
Reserved
A8
A7
7
Op Mode
A5
A6
A4
5
6
A3
3
4
CAS Latency
Program
BA1, BA0 = “0, 0”
to ensure compatibility
with future devices.
A0
0
Address Bus
Mode Register (Mx)
Burst Length
Burst Length
M2 M1 M0
Write Burst Mode
M9
1
2
BT
A1
A2
0
Programmed Burst Length
1
Single Location Access
M3 = 0
M3 = 1
0
0
0
1
1
0
0
1
2
2
0
1
0
4
4
0
1
1
8
8
1
0
0
Reserved
Reserved
M8
M7
M6-M0
Operating Mode
1
0
1
Reserved
Reserved
0
0
Defined
Standard Operation
1
1
0
Reserved
Reserved
–
–
–
All other states reserved
1
1
1
Full Page
Reserved
M3
0
Sequential
1
Interleaved
CAS Latency
M6 M5 M4
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Burst Type
0
0
0
Reserved
0
0
1
1
0
1
0
2
0
1
1
3
1
0
0
Reserved
1
0
1
Reserved
1
1
0
Reserved
1
1
1
Reserved
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Mode Register
Burst Length
Read and write accesses to the device are burst oriented, and the burst length (BL) is
programmable. The burst length determines the maximum number of column locations that can be accessed for a given READ or WRITE command. Burst lengths of 1, 2,
4, 8, or continuous locations are available for both the sequential and the interleaved
burst types, and a continuous page burst is available for the sequential type. The continuous page burst is used in conjunction with the BURST TERMINATE command to
generate arbitrary burst lengths.
Reserved states should not be used, as unknown operation or incompatibility with future versions may result.
When a READ or WRITE command is issued, a block of columns equal to the burst
length is effectively selected. All accesses for that burst take place within this block,
meaning that the burst wraps within the block when a boundary is reached. The block
is uniquely selected by A[8:1] when BL = 2, A[8:2] when BL = 4, and A[8:3] when BL = 8.
The remaining (least significant) address bit(s) is (are) used to select the starting location within the block. Continuous page bursts wrap within the page when the boundary
is reached.
Burst Type
Accesses within a given burst can be programmed to be either sequential or interleaved;
this is referred to as the burst type and is selected via bit M3.
The ordering of accesses within a burst is determined by the burst length, the burst
type, and the starting column address.
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Mode Register
Table 18: Burst Definition Table
Order of Accesses Within a Burst
Burst Length
Starting Column Address
2
Type = Interleaved
0
0-1
0-1
1
1-0
1-0
A0
4
8
Type = Sequential
A1
A0
0
0
0-1-2-3
0-1-2-3
0
1
1-2-3-0
1-0-3-2
1
0
2-3-0-1
2-3-0-1
1
1
3-0-1-2
3-2-1-0
A2
A1
A0
0
0
0
0-1-2-3-4-5-6-7
0-1-2-3-4-5-6-7
0
0
1
1-2-3-4-5-6-7-0
1-0-3-2-5-4-7-6
0
1
0
2-3-4-5-6-7-0-1
2-3-0-1-6-7-4-5
0
1
1
3-4-5-6-7-0-1-2
3-2-1-0-7-6-5-4
1
0
0
4-5-6-7-0-1-2-3
4-5-6-7-0-1-2-3
1
0
1
5-6-7-0-1-2-3-4
5-4-7-6-1-0-3-2
1
1
0
6-7-0-1-2-3-4-5
6-7-4-5-2-3-0-1
1
1
1
7-0-1-2-3-4-5-6
7-6-5-4-3-2-1-0
Cn, Cn + 1, Cn + 2, Cn + 3...Cn - 1,
Cn...
Not supported
Continuous
n = A0–An/9/8 (location 0–y)
Notes:
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1. For full-page accesses: y = 2048 (x4); y = 1024 (x8); y = 512 (x16).
2. For BL = 2, A1–A9, A11 (x4); A1–A9 (x8); or A1–A8 (x16) select the block-of-two burst; A0
selects the starting column within the block.
3. For BL = 4, A2–A9, A11 (x4); A2–A9 (x8); or A2–A8 (x16) select the block-of-four burst;
A0–A1 select the starting column within the block.
4. For BL = 8, A3–A9, A11 (x4); A3–A9 (x8); or A3–A8 (x16) select the block-of-eight burst;
A0–A2 select the starting column within the block.
5. For a full-page burst, the full row is selected and A0–A9, A11 (x4); A0–A9 (x8); or A0–A8
(x16) select the starting column.
6. Whenever a boundary of the block is reached within a given sequence above, the following access wraps within the block.
7. For BL = 1, A0–A9, A11 (x4); A0–A9 (x8); or A0–A8 (x16) select the unique column to be
accessed, and mode register bit M3 is ignored.
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Mode Register
CAS Latency
The CAS latency (CL) is the delay, in clock cycles, between the registration of a READ
command and the availability of the output data. The latency can be set to two or three
clocks.
If a READ command is registered at clock edge n, and the latency is m clocks, the data
will be available by clock edge n + m. The DQ start driving as a result of the clock edge
one cycle earlier (n + m - 1), and provided that the relevant access times are met, the
data is valid by clock edge n + m. For example, assuming that the clock cycle time is
such that all relevant access times are met, if a READ command is registered at T0 and
the latency is programmed to two clocks, the DQ start driving after T1 and the data is
valid by T2.
Reserved states should not be used as unknown operation or incompatibility with future versions may result.
Figure 20: CAS Latency
T0
T1
T2
T3
NOP
NOP
CLK
Command
READ
tOH
tLZ
DOUT
DQ
tAC
CL = 2
T0
T1
T2
T3
NOP
NOP
NOP
T4
CLK
Command
READ
tOH
tLZ
DOUT
DQ
tAC
CL = 3
Don’t Care
Undefined
Operating Mode
The normal operating mode is selected by setting M7 and M8 to zero; the other combinations of values for M7 and M8 are reserved for future use. Reserved states should not
be used because unknown operation or incompatibility with future versions may result.
Write Burst Mode
When M9 = 0, the burst length programmed via M[2:0] applies to both READ and
WRITE bursts; when M9 = 1, the programmed burst length applies to READ bursts, but
write accesses are single-location (nonburst) accesses.
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Bank/Row Activation
Bank/Row Activation
Before any READ or WRITE commands can be issued to a bank within the SDRAM, a
row in that bank must be opened. This is accomplished via the ACTIVE command,
which selects both the bank and the row to be activated.
After a row is opened with the ACTIVE command, a READ or WRITE command can be
issued to that row, subject to the tRCD specification. tRCD (MIN) should be divided by
the clock period and rounded up to the next whole number to determine the earliest
clock edge after the ACTIVE command on which a READ or WRITE command can be
entered. For example, a tRCD specification of 20ns with a 125 MHz clock (8ns period)
results in 2.5 clocks, rounded to 3. This is reflected in Figure 21 (page 49), which covers
any case where 2 < tRCD (MIN)/tCK ≤ 3. (The same procedure is used to convert other
specification limits from time units to clock cycles.)
A subsequent ACTIVE command to a different row in the same bank can only be issued
after the previous active row has been precharged. The minimum time interval between
successive ACTIVE commands to the same bank is defined by tRC.
A subsequent ACTIVE command to another bank can be issued while the first bank is
being accessed, which results in a reduction of total row-access overhead. The minimum time interval between successive ACTIVE commands to different banks is defined
by tRRD.
Figure 21: Example: Meeting tRCD (MIN) When 2 < tRCD (MIN)/tCK < 3
T0
T1
T2
T3
CLK
tCK
Command
ACTIVE
tCK
NOP
tCK
NOP
READ or
WRITE
tRCD(MIN)
Don’t Care
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READ Operation
READ Operation
READ bursts are initiated with a READ command, as shown in Figure 15 (page 33). The
starting column and bank addresses are provided with the READ command, and auto
precharge is either enabled or disabled for that burst access. If auto precharge is enabled, the row being accessed is precharged at the completion of the burst. In the following figures, auto precharge is disabled.
During READ bursts, the valid data-out element from the starting column address is
available following the CAS latency after the READ command. Each subsequent dataout element will be valid by the next positive clock edge. Figure 23 (page 52) shows
general timing for each possible CAS latency setting.
Upon completion of a burst, assuming no other commands have been initiated, the DQ
signals will go to High-Z. A continuous page burst continues until terminated. At the
end of the page, it wraps to column 0 and continues.
Data from any READ burst can be truncated with a subsequent READ command, and
data from a fixed-length READ burst can be followed immediately by data from a READ
command. In either case, a continuous flow of data can be maintained. The first data
element from the new burst either follows the last element of a completed burst or the
last desired data element of a longer burst that is being truncated. The new READ command should be issued x cycles before the clock edge at which the last desired data element is valid, where x = CL - 1. This is shown in Figure 23 (page 52) for CL2 and CL3.
SDRAM devices use a pipelined architecture and therefore do not require the 2n rule associated with a prefetch architecture. A READ command can be initiated on any clock
cycle following a READ command. Full-speed random read accesses can be performed
to the same bank, or each subsequent READ can be performed to a different bank.
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READ Operation
Figure 22: Consecutive READ Bursts
T0
T1
T2
T3
T4
T5
T6
CLK
Command
READ
NOP
NOP
NOP
NOP
READ
NOP
X = 1 cycle
Address
Bank,
Col n
Bank,
Col b
DOUT
n+2
DOUT
n+1
DOUT
n
DQ
DOUT
n+3
DOUT
b
CL = 2
T0
T1
T2
T3
T4
T5
T6
T7
CLK
Command
READ
NOP
NOP
NOP
READ
NOP
NOP
NOP
X = 2 cycles
Address
Bank,
Col n
Bank,
Col b
DOUT
DQ
CL = 3
Note:
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DOUT
DOUT
Transitioning data
DOUT
DOUT
Don’t Care
1. Each READ command can be issued to any bank. DQM is LOW.
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READ Operation
Figure 23: Random READ Accesses
T0
T1
T2
T3
T4
Command
READ
READ
READ
READ
Address
Bank,
Col n
Bank,
Col a
Bank,
Col x
Bank,
Col m
T5
CLK
DOUT
DQ
NOP
DOUT
NOP
DOUT
DOUT
CL = 2
T0
T1
T2
T3
T4
Command
READ
READ
READ
READ
Address
Bank,
Col n
Bank,
Col a
Bank,
Col x
Bank,
Col m
T5
T6
CLK
NOP
DOUT
DQ
DOUT
NOP
DOUT
NOP
DOUT
CL = 3
Transitioning data
Note:
Don’t Care
1. Each READ command can be issued to any bank. DQM is LOW.
Data from any READ burst can be truncated with a subsequent WRITE command, and
data from a fixed-length READ burst can be followed immediately by data from a
WRITE command (subject to bus turnaround limitations). The WRITE burst can be initiated on the clock edge immediately following the last (or last desired) data element
from the READ burst, provided that I/O contention can be avoided. In a given system
design, there is a possibility that the device driving the input data will go Low-Z before
the DQ go High-Z. In this case, at least a single-cycle delay should occur between the
last read data and the WRITE command.
The DQM input is used to avoid I/O contention, as shown in Figure 24 (page 53) and
Figure 25 (page 54). The DQM signal must be asserted (HIGH) at least two clocks prior
to the WRITE command (DQM latency is two clocks for output buffers) to suppress data-out from the READ. After the WRITE command is registered, the DQ will go to High-Z
(or remain High-Z), regardless of the state of the DQM signal, provided the DQM was
active on the clock just prior to the WRITE command that truncated the READ command. If not, the second WRITE will be an invalid WRITE. For example, if DQM was
LOW during T4, then the WRITEs at T5 and T7 would be valid, and the WRITE at T6
would be invalid.
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READ Operation
The DQM signal must be de-asserted prior to the WRITE command (DQM latency is
zero clocks for input buffers) to ensure that the written data is not masked. Figure 24
(page 53) shows where, due to the clock cycle frequency, bus contention is avoided
without having to add a NOP cycle, while Figure 25 (page 54) shows the case where an
additional NOP cycle is required.
A fixed-length READ burst may be followed by or truncated with a PRECHARGE command to the same bank, provided that auto precharge was not activated. The PRECHARGE command should be issued x cycles before the clock edge at which the last desired data element is valid, where x = CL - 1. This is shown in Figure 26 (page 54) for
each possible CL; data element n + 3 is either the last of a burst of four or the last desired data element of a longer burst. Following the PRECHARGE command, a subsequent command to the same bank cannot be issued until tRP is met. Note that part of
the row precharge time is hidden during the access of the last data element(s).
In the case of a fixed-length burst being executed to completion, a PRECHARGE command issued at the optimum time (as described above) provides the same operation
that would result from the same fixed-length burst with auto precharge. The disadvantage of the PRECHARGE command is that it requires that the command and address
buses be available at the appropriate time to issue the command. The advantage of the
PRECHARGE command is that it can be used to truncate fixed-length or continuous
page bursts.
Figure 24: READ-to-WRITE
T0
T1
T2
T3
T4
CLK
DQM
Command
READ
Address
Bank,
Col n
NOP
NOP
NOP
WRITE
Bank,
Col b
tCK
tHZ
DOUT
DQ
DIN
t
DS
Transitioning data
Note:
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Don’t Care
1. CL = 3. The READ command can be issued to any bank, and the WRITE command can be
to any bank. If a burst of one is used, DQM is not required.
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READ Operation
Figure 25: READ-to-WRITE With Extra Clock Cycle
T0
T1
T2
T3
T4
T5
CLK
DQM
Command
Address
READ
NOP
NOP
NOP
NOP
WRITE
Bank,
Col n
Bank,
Col b
tHZ
DOUT
DQ
DIN
tDS
Transitioning data
Note:
Don’t Care
1. CL = 3. The READ command can be issued to any bank, and the WRITE command can be
to any bank.
Figure 26: READ-to-PRECHARGE
T0
T1
T2
T3
T4
T5
T6
T7
CLK
tRP
Command
READ
Address
Bank a,
Col n
NOP
NOP
NOP
NOP
PRECHARGE
NOP
ACTIVE
X = 1 cycle
Bank
(a or all)
DOUT
DQ
Bank a,
Row
DOUT
DOUT
DOUT
CL = 2
T0
T1
T2
T3
T4
T5
T6
T7
CLK
t RP
Command
READ
NOP
NOP
NOP
PRECHARGE
NOP
NOP
ACTIVE
X = 2 cycles
Address
Bank
(a or all)
Bank a,
Col
DOUT
DQ
DOUT
Bank a,
Row
DOUT
DOUT
CL = 3
Transitioning data
Note:
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Don’t Care
1. DQM is LOW.
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READ Operation
Continuous-page READ bursts can be truncated with a BURST TERMINATE command
and fixed-length READ bursts can be truncated with a BURST TERMINATE command,
provided that auto precharge was not activated. The BURST TERMINATE command
should be issued x cycles before the clock edge at which the last desired data element is
valid, where x = CL - 1. This is shown in Figure 27 (page 55) for each possible CAS latency; data element n + 3 is the last desired data element of a longer burst.
Figure 27: Terminating a READ Burst
T0
T1
T2
T3
T4
T5
T6
CLK
Command
READ
Address
Bank,
Col n
NOP
NOP
NOP
BURST
TERMINATE
NOP
NOP
X = 1 cycle
DOUT
DQ
DOUT
DOUT
DOUT
CL = 2
T0
T1
T2
T3
T4
T5
T6
T7
CLK
Command
READ
Address
Bank,
Col n
NOP
NOP
NOP
BURST
TERMINATE
NOP
NOP
NOP
X = 2 cycles
DOUT
DQ
DOUT
DOUT
DOUT
CL = 3
Transitioning data
Note:
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Don’t Care
1. DQM is LOW.
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READ Operation
Figure 28: Alternating Bank Read Accesses
T0
T1
tCK
CLK
T2
T3
T4
T5
T6
T7
T8
READ
NOP
ACTIVE
tCL
tCH
tCKS
tCKH
tCMS
tCMH
CKE
Command
ACTIVE
NOP
READ
ACTIVE
NOP
NOP
tCMS tCMH
DQM
tAS
Address
Row
tAS
A10
Row
Column m
tAH
Column b
Enable auto precharge
1
Row
Enable auto precharge
Row
tAS
BA0, BA1
tAH
Row
Row
tAH
Bank 0
Bank 0
Bank 3
Bank 3
tAC
tOH
tAC
DQ
tLZ
tRCD - bank 0
tAC
tOH
DOUT
DOUT
Bank 0
tAC
tOH
DOUT
tAC
tOH
DOUT
tRP - bank 0
CL - bank 0
tAC
tOH
DOUT
tRCD - bank 0
tRAS - bank 0
tRC - bank 0
tRRD
tRCD - bank 3
CL - bank 3
Don’t Care
Note:
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Undefined
1. For this example, BL = 4 and CL = 2.
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READ Operation
Figure 29: READ Continuous Page Burst
T0
T1
T2
tCL
CLK
T3
T4
T5
T6
((
))
((
))
tCK
tCH
Tn + 1
Tn + 2
Tn + 3
Tn + 4
tCKS tCKH
((
))
((
))
CKE
tCMS
Command
tCMH
ACTIVE
NOP
READ
tCMS
NOP
NOP
NOP
NOP
tCMH
tAS
tAS
A10
BURST TERM
NOP
NOP
((
))
((
))
Column m
tAH
((
))
((
))
Row
tAS
BA0, BA1
tAH
Row
NOP
((
))
((
))
DQM
Address
((
))
((
))
tAH
Bank
((
))
((
))
Bank
tAC
tAC
tOH
DOUT
DQ
DOUT
tLZ
tRCD
CAS latency
tAC
tOH
tAC
tOH
((
))
((
DOUT ) )
((
))
tAC
tOH
DOUT
Full-page burst does not self-terminate.
Can use BURST TERMINATE command.
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DOUT
tOH
DOUT
tHZ
All locations within same row
Full page completed
Note:
tAC
tOH
Don’t Care
Undefined
1. For this example, CL = 2.
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READ Operation
Figure 30: READ – DQM Operation
T0
T1
tCK
CLK
T2
T3
T4
T5
NOP
NOP
T6
T7
T8
NOP
NOP
tCL
tCH
tCKS
tCKH
tCMS
tCMH
CKE
Command
ACTIVE
NOP
READ
tCMS
NOP
NOP
tCMH
DQM
tAS
Row
Address
tAS
Column m
tAH
Enable auto precharge
Row
A10
tAS
BA0, BA1
tAH
Disable auto precharge
tAH
Bank
Bank
tAC
tOH
tAC
DQ
DOUT
tLZ
tRCD
tHZ
CL = 2
tAC
tLZ
tOH
tOH
DOUT
DOUT
tHZ
Don’t Care
Undefined
Note:
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1. For this example, BL = 4 and CL = 2.
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WRITE Operation
WRITE Operation
WRITE bursts are initiated with a WRITE command, as shown in Figure 16 (page 34).
The starting column and bank addresses are provided with the WRITE command and
auto precharge is either enabled or disabled for that access. If auto precharge is enabled, the row being accessed is precharged at the completion of the burst. For the generic WRITE commands used in the following figures, auto precharge is disabled.
During WRITE bursts, the first valid data-in element is registered coincident with the
WRITE command. Subsequent data elements are registered on each successive positive
clock edge. Upon completion of a fixed-length burst, assuming no other commands
have been initiated, the DQ will remain at High-Z and any additional input data will be
ignored (see Figure 31 (page 59)). A continuous page burst continues until terminated;
at the end of the page, it wraps to column 0 and continues.
Data for any WRITE burst can be truncated with a subsequent WRITE command, and
data for a fixed-length WRITE burst can be followed immediately by data for a WRITE
command. The new WRITE command can be issued on any clock following the previous WRITE command, and the data provided coincident with the new command applies to the new command (see Figure 32 (page 60)). Data n + 1 is either the last of a
burst of two or the last desired data element of a longer burst.
SDRAM devices use a pipelined architecture and therefore do not require the 2n rule associated with a prefetch architecture. A WRITE command can be initiated on any clock
cycle following a previous WRITE command. Full-speed random write accesses within a
page can be performed to the same bank, as shown in Figure 33 (page 61), or each
subsequent WRITE can be performed to a different bank.
Figure 31: WRITE Burst
T0
T1
T2
T3
Command
WRITE
NOP
NOP
NOP
Address
Bank,
Col n
CLK
DQ
DIN
DIN
Transitioning data
Note:
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Don’t Care
1. BL = 2. DQM is LOW.
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WRITE Operation
Figure 32: WRITE-to-WRITE
T0
T1
T2
Command
WRITE
NOP
WRITE
Address
Bank,
Col n
CLK
DQ
DIN
Bank,
Col b
DIN
Transitioning data
Note:
DIN
Don’t Care
1. DQM is LOW. Each WRITE command may be issued to any bank.
Data for any WRITE burst can be truncated with a subsequent READ command, and
data for a fixed-length WRITE burst can be followed immediately by a READ command.
After the READ command is registered, data input is ignored and WRITEs will not be
executed (see Figure 34 (page 61)). Data n + 1 is either the last of a burst of two or the
last desired data element of a longer burst.
Data for a fixed-length WRITE burst can be followed by or truncated with a PRECHARGE command to the same bank, provided that auto precharge was not activated.
A continuous-page WRITE burst can be truncated with a PRECHARGE command to the
same bank. The PRECHARGE command should be issued tWR after the clock edge at
which the last desired input data element is registered. The auto precharge mode requires a tWR of at least one clock with time to complete, regardless of frequency.
In addition, when truncating a WRITE burst at high clock frequencies ( tCK < 15ns), the
DQM signal must be used to mask input data for the clock edge prior to and the clock
edge coincident with the PRECHARGE command (see Figure 35 (page 62)). Data n + 1
is either the last of a burst of two or the last desired data element of a longer burst. Following the PRECHARGE command, a subsequent command to the same bank cannot
be issued until tRP is met.
In the case of a fixed-length burst being executed to completion, a PRECHARGE command issued at the optimum time (as described above) provides the same operation
that would result from the same fixed-length burst with auto precharge. The disadvantage of the PRECHARGE command is that it requires that the command and address
buses be available at the appropriate time to issue the command. The advantage of the
PRECHARGE command is that it can be used to truncate fixed-length bursts or continuous page bursts.
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WRITE Operation
Figure 33: Random WRITE Cycles
T0
T1
T2
T3
Command
WRITE
WRITE
WRITE
WRITE
Address
Bank,
Col n
Bank,
Col a
Bank,
Col x
Bank,
Col m
DIN
DIN
DIN
DIN
CLK
DQ
Transitioning data
Note:
Don’t Care
1. Each WRITE command can be issued to any bank. DQM is LOW.
Figure 34: WRITE-to-READ
T0
T1
T2
Command
WRITE
NOP
READ
Address
Bank,
Col n
T3
T4
T5
NOP
NOP
NOP
DOUT
DOUT
CLK
DQ
DIN
Bank,
Col b
DIN
Transitioning data
Note:
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Don’t Care
1. The WRITE command can be issued to any bank, and the READ command can be to any
bank. DQM is LOW. CL = 2 for illustration.
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WRITE Operation
Figure 35: WRITE-to-PRECHARGE
T0
T1
T2
T3
T4
T5
T6
NOP
ACTIVE
NOP
CLK
tWR @ tCK ≥ 15ns
DQM
tRP
Command
Address
WRITE
NOP
NOP
PRECHARGE
Bank
(a or all)
Bank a,
Col n
Bank a,
Row
tWR
DQ
DIN
DIN
tWR @ tCK < 15ns
DQM
tRP
Command
Address
WRITE
NOP
NOP
PRECHARGE
NOP
NOP
Bank
(a or all)
Bank a,
Col n
ACTIVE
Bank a,
Row
t WR
DQ
DIN
DIN
Transitioning data
Note:
Don’t Care
1. In this example DQM could remain LOW if the WRITE burst is a fixed length of two.
Fixed-length WRITE bursts can be truncated with the BURST TERMINATE command.
When truncating a WRITE burst, the input data applied coincident with the BURST
TERMINATE command is ignored. The last data written (provided that DQM is LOW at
that time) will be the input data applied one clock previous to the BURST TERMINATE
command. This is shown in Figure 36 (page 63), where data n is the last desired data
element of a longer burst.
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WRITE Operation
Figure 36: Terminating a WRITE Burst
T0
T1
Command
WRITE
BURST
TERMINATE
Address
Bank,
Col n
T2
CLK
DQ
DIN
Transitioning data
Note:
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NEXT
COMMAND
Address
Data
Don’t Care
1. DQM is LOW.
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WRITE Operation
Figure 37: Alternating Bank Write Accesses
T0
T1
tCK
CLK
T2
T3
T4
T5
T6
T7
T8
T9
WRITE
NOP
NOP
ACTIVE
tCL
tCH
tCKS
tCKH
tCMS
tCMH
CKE
Command
ACTIVE
NOP
WRITE
tCMS
NOP
NOP
ACTIVE
tCMH
DQM
tAS
Address
tAS
A10
Row
Column m
tAH
Row
Column b
Enable auto precharge
Enable auto precharge
Row
tAS
BA0, BA1
tAH
Row
Row
Row
tAH
Bank 0
Bank 0
tDS
tDH
DIN
DQ
Bank 1
tDS
tDH
DIN
tDS
Bank 1
tDS
tDH
DIN
tDH
DIN
tDS
tDH
DIN
tWR - bank 0
tRCD - bank 0
Bank 0
tDS
tDH
DIN
tDS
tDH
DIN
tRP - bank 0
tDS
tDH
DIN
tRCD - bank 0
tRAS - bank 0
tWR - bank 1
tRC - bank 0
tRCD - bank 1
tRRD
Don’t Care
Note:
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1. For this example, BL = 4.
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WRITE Operation
Figure 38: WRITE – Continuous Page Burst
T0
T1
T2
tCL
CLK
T3
T4
T5
((
))
((
))
tCK
tCH
tCKS
tCKH
Command
tCMH
ACTIVE
NOP
WRITE
NOP
NOP
NOP
tCMS tCMH
Address
A10
((
))
((
))
NOP
tAH
NOP
((
))
((
))
tAH
Bank
((
))
((
))
Bank
tDS
DIN
DQ
tDH
tDS
tDH
tDS
DIN
tDH
DIN
tRCD
tDS
tDH
DIN
((
))
((
))
tDS
All locations within same row
tDH
DIN
Full-page burst
does not self-terminate.
Use BURST TERMINATE
command to stop.1, 2
Full page completed
Notes:
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BURST TERM
((
))
((
))
Column m
Row
tAS
BA0, BA1
tAH
Row
tAS
Tn + 3
((
))
((
))
DQM
tAS
Tn + 2
((
))
((
))
CKE
tCMS
Tn + 1
Don’t Care
1. tWR must be satisfied prior to issuing a PRECHARGE command.
2. Page left open; no tRP.
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WRITE Operation
Figure 39: WRITE – DQM Operation
T0
T1
T2
tCK
CLK
T3
T4
T5
NOP
NOP
NOP
T6
T7
NOP
NOP
tCL
tCH
tCKS
tCKH
tCMS
tCMH
CKE
Command
ACTIVE
NOP
WRITE
tCMS tCMH
DQM
tAS
Address
Row
tAS
A10
Column m
tAH
Enable auto precharge
Row
tAS
BA0, BA1
tAH
Disable auto precharge
tAH
Bank
Bank
tDS
tDH
tDS
DIN
DQ
DIN
tRCD
Note:
tDH
tDS
tDH
DIN
Don’t Care
1. For this example, BL = 4.
Burst Read/Single Write
The burst read/single write mode is entered by programming the write burst mode bit
(M9) in the mode register to a 1. In this mode, all WRITE commands result in the access
of a single column location (burst of one), regardless of the programmed burst length.
READ commands access columns according to the programmed burst length and sequence, just as in the normal mode of operation (M9 = 0).
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PRECHARGE Operation
PRECHARGE Operation
The PRECHARGE command (see Figure 17 (page 35)) is used to deactivate the open row
in a particular bank or the open row in all banks. The bank(s) will be available for a subsequent row access some specified time (tRP) after the PRECHARGE command is issued. Input A10 determines whether one or all banks are to be precharged, and in the
case where only one bank is to be precharged (A10 = LOW), inputs BA0 and BA1 select
the bank. When all banks are to be precharged (A10 = HIGH), inputs BA0 and BA1 are
treated as “Don’t Care.” After a bank has been precharged, it is in the idle state and
must be activated prior to any READ or WRITE commands being issued to that bank.
Auto Precharge
Auto precharge is a feature that performs the same individual-bank PRECHARGE function described previously, without requiring an explicit command. This is accomplished
by using A10 to enable auto precharge in conjunction with a specific READ or WRITE
command. A precharge of the bank/row that is addressed with the READ or WRITE
command is automatically performed upon completion of the READ or WRITE burst,
except in the continuous page burst mode where auto precharge does not apply. In the
specific case of write burst mode set to single location access with burst length set to
continuous, the burst length setting is the overriding setting and auto precharge does
not apply. Auto precharge is nonpersistent in that it is either enabled or disabled for
each individual READ or WRITE command.
Auto precharge ensures that the precharge is initiated at the earliest valid stage within a
burst. Another command cannot be issued to the same bank until the precharge time
(tRP) is completed. This is determined as if an explicit PRECHARGE command was issued at the earliest possible time, as described for each burst type in the Burst Type
(page 46) section.
Micron SDRAM supports concurrent auto precharge; cases of concurrent auto precharge for READs and WRITEs are defined below.
READ with auto precharge interrupted by a READ (with or without auto precharge)
A READ to bank m will interrupt a READ on bank n following the programmed CAS latency. The precharge to bank n begins when the READ to bank m is registered (see Figure 40 (page 68)).
READ with auto precharge interrupted by a WRITE (with or without auto precharge)
A WRITE to bank m will interrupt a READ on bank n when registered. DQM should be
used two clocks prior to the WRITE command to prevent bus contention. The precharge to bank n begins when the WRITE to bank m is registered (see Figure 41
(page 69)).
WRITE with auto precharge interrupted by a READ (with or without auto precharge)
A READ to bank m will interrupt a WRITE on bank n when registered, with the data-out
appearing CL later. The precharge to bank n will begin after tWR is met, where tWR begins when the READ to bank m is registered. The last valid WRITE to bank n will be data-in registered one clock prior to the READ to bank m (see Figure 46 (page 74)).
WRITE with auto precharge interrupted by a WRITE (with or without auto precharge)
A WRITE to bank m will interrupt a WRITE on bank n when registered. The precharge to
bank n will begin after tWR is met, where tWR begins when the WRITE to bank m is reg-
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PRECHARGE Operation
istered. The last valid data WRITE to bank n will be data registered one clock prior to a
WRITE to bank m (see Figure 47 (page 74)).
Figure 40: READ With Auto Precharge Interrupted by a READ
T0
T1
T2
T3
T4
T5
T6
T7
CLK
Command
Bank n
Internal
states
NOP
Page active
READ - AP
Bank n
READ - AP
Bank m
NOP
READ with burst of 4
NOP
NOP
NOP
Interrupt burst, precharge
Idle
tRP - bank n
Bank m
Page active
Address
Bank n,
Col a
NOP
tRP - bank m
Precharge
READ with burst of 4
Bank m,
Col d
DOUT
DQ
DOUT
DOUT
DOUT
CL = 3 (bank n)
CL = 3 (bank m)
Don’t Care
Note:
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1. DQM is LOW.
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PRECHARGE Operation
Figure 41: READ With Auto Precharge Interrupted by a WRITE
T0
T1
T2
T3
T4
T5
T6
T7
CLK
Command
Internal
States
Bank n
READ - AP
Bank n
Page
active
NOP
NOP
NOP
READ with burst of 4
WRITE - AP
Bank m
NOP
NOP
Interrupt burst, precharge
Idle
tWR - bankm
tRP - bank n
Page active
Bank m
Address
NOP
Write-back
WRITE with burst of 4
Bank n,
Col a
Bank m,
Col d
DQM1
DOUT
DQ
CL = 3 (bank n)
Note:
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DIN
DIN
DIN
Transitioning data
DIN
Don’t Care
1. DQM is HIGH at T2 to prevent DOUTa + 1 from contending with DINd at T4.
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PRECHARGE Operation
Figure 42: READ With Auto Precharge
T0
T1
tCK
CLK
T2
T3
T4
T5
NOP
NOP
T6
T7
T8
NOP
NOP
ACTIVE
tCL
tCH
tCKS
tCKH
tCMS
tCMH
CKE
Command
ACTIVE
NOP
READ
tCMS
NOP
tCMH
DQM
tAS
Address
Row
tAS
A10
Row
Column m
tAH
Enable auto precharge
Row
tAS
BA0, BA1
tAH
Row
tAH
Bank
Bank
Bank
tAC
tOH
tAC
DQ
tLZ
tRCD
DOUT m
tAC
tOH
DOUT
m+1
tAC
tOH
DOUT
m+2
tRP
CL = 2
tOH
DOUT
m+3
tHZ
tRAS
tRC
Don’t Care
Note:
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Undefined
1. For this example, BL = 4 and CL = 2.
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PRECHARGE Operation
Figure 43: READ Without Auto Precharge
T0
T1
tCK
CLK
T2
T3
T4
T5
NOP
NOP
T6
T7
T8
NOP
ACTIVE
tCL
tCH
tCKS
tCKH
CKE
tCMS tCMH
Command
ACTIVE
NOP
READ
NOP
PRECHARGE
tCMS tCMH
DQM
tAS
Row
Address
tAS
Row
Column m
tAH
All banks
Row
A10
tAS
BA0, BA1
tAH
Row
tAH
Bank
Disable auto precharge
Single bank
Bank
Bank(s)
tAC
tOH
tAC
DQ
tLZ
tRCD
DOUT
tOH
DOUT
Bank
tAC
tAC
tOH
DOUT
tRP
CL = 2
tOH
DOUT
tHZ
tRAS
tRC
Don’t Care
Note:
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Undefined
1. For this example, BL = 4, CL = 2, and the READ burst is followed by a manual PRECHARGE.
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PRECHARGE Operation
Figure 44: Single READ With Auto Precharge
T0
T1
T2
tCK
CLK
T3
T4
T5
NOP
NOP
T6
T7
tCL
tCH
tCKS
tCKH
tCMS
tCMH
CKE
Command
ACTIVE
NOP
READ
NOP
NOP
ACTIVE
tCMS tCMH
DQM
tAS
tAH
tAS
tAH
Enable auto precharge
Row
Row
A10
tAS
BA0, BA1
Row
Column m
Row
Address
tAH
Bank
Bank
Bank
tAC
DQ
DOUT
tLZ
tRCD
tRAS
tOH
tRP
CL = 2
tRC
Don’t Care
Note:
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Undefined
1. For this example, BL = 1 and CL = 2.
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PRECHARGE Operation
Figure 45: Single READ Without Auto Precharge
T0
T1
tCK
CLK
T2
T3
T4
T5
NOP
NOP
T6
T7
T8
tCL
tCH
tCKS
tCKH
tCMS
tCMH
CKE
Command
ACTIVE
NOP
READ
PRECHARGE
NOP
ACTIVE
NOP
tCMS tCMH
DQM
tAS
Address
A10
Row
Column m
Row
tAS
tAH
All banks
Row
Row
tAS
BA0, BA1
tAH
Single bank
Disable auto precharge
tAH
Bank
Bank(s)
Bank
DQ
tLZ
tRCD
DOUT
tHZ
CL = 2
tRP
Don’t Care
tRAS
tRC
Undefined
Note:
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Bank
tOH
tAC
1. For this example, BL = 1, CL = 2, and the READ burst is followed by a manual PRECHARGE.
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PRECHARGE Operation
Figure 46: WRITE With Auto Precharge Interrupted by a READ
T0
T1
T2
T3
T4
T5
T6
T7
CLK
Command
Bank n
NOP
Page active
WRITE - AP
Bank n
READ - AP
Bank m
NOP
NOP
NOP
Interrupt burst, write-back
WRITE with burst of 4
Internal
States
Page active
Address
Bank n,
Col a
DIN
DQ
NOP
Precharge
tRP - bank n
t WR - bank n
Bank m
NOP
tRP - bank m
READ with burst of 4
Bank m,
Col d
DIN
DOUT
DOUT
CL = 3 (bank m)
Don’t Care
Note:
1. DQM is LOW.
Figure 47: WRITE With Auto Precharge Interrupted by a WRITE
T0
T1
T2
T3
T4
T5
T6
T7
CLK
Command
Bank n
Internal
States
NOP
Page active
WRITE - AP
Bank n
NOP
NOP
WRITE with burst of 4
WRITE - AP
Bank m
NOP
Interrupt burst, write-back
Address
DQ
Page active
DIN
Precharge
tWR - bank m
Write-back
WRITE with burst of 4
Bank n,
Col a
NOP
tRP - bank n
tWR - bank n
Bank m
NOP
Bank m,
Col d
DIN
DIN
DIN
DIN
DIN
DIN
Don’t Care
Note:
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1. DQM is LOW.
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PRECHARGE Operation
Figure 48: WRITE With Auto Precharge
T0
tCK
CLK
T1
tCL
T2
T3
T4
T5
T6
T7
T8
T9
NOP
NOP
NOP
NOP
NOP
NOP
ACTIVE
tCH
tCKS
tCKH
tCMS
tCMH
CKE
Command
ACTIVE
NOP
WRITE
tCMS tCMH
DQM
tAS
Address
Row
tAS
A10
Row
Column m
tAH
Enable auto precharge
Row
Row
tAS
BA0, BA1
tAH
tAH
Bank
Bank
Bank
tDS
tDH
DIN
DQ
tDS
tDH
DIN
tDS
tDH
DIN
tDS
tDH
DIN
tRCD
tRAS
tWR
tRP
tRC
Don’t Care
Note:
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1. For this example, BL = 4.
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PRECHARGE Operation
Figure 49: WRITE Without Auto Precharge
T0
tCK
CLK
T1
tCL
T2
T3
T4
T5
T6
NOP
NOP
NOP
NOP
T7
T8
T9
PRECHARGE
NOP
ACTIVE
tCH
tCKS
tCKH
tCMS
tCMH
CKE
Command
ACTIVE
NOP
WRITE
tCMS tCMH
DQM
tAS
Address
Row
tAS
A10
Column m
Row
tAH
All banks
Row
Row
tAS
BA0, BA1
tAH
tAH
Bank
Disable auto precharge
Single bank
Bank
Bank
tDS
tDH
DIN
DQ
tDS
tDH
DIN
tDS
tDH
DIN
tDS
Bank
tDH
DIN
tRCD
tRAS
tWR
tRP
tRC
Don’t Care
Note:
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1. For this example, BL = 4 and the WRITE burst is followed by a manual PRECHARGE.
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PRECHARGE Operation
Figure 50: Single WRITE With Auto Precharge
T0
tCK
CLK
T1
T2
tCL
T3
T4
T5
T6
NOP
NOP
NOP
NOP
T7
T8
ACTIVE
NOP
tCH
tCKS
tCKH
tCMS
tCMH
CKE
Command
ACTIVE
NOP
WRITE
tCMS tCMH
DQM
tAS
Address
Row
tAS
A10
Row
Column m
tAH
Enable auto precharge
Row
Row
tAS
BA0, BA1
tAH
tAH
Bank
Bank
Bank
tDS
tDH
DIN
DQ
tRCD
tRAS
tRP
tWR
tRC
Don’t Care
Note:
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1. For this example, BL = 1.
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PRECHARGE Operation
Figure 51: Single WRITE Without Auto Precharge
T0
T1
tCK
CLK
T2
T3
T4
NOP
NOP
T5
T6
T7
T8
tCL
tCH
tCKS
tCKH
tCMS
tCMH
CKE
Command
ACTIVE
NOP
WRITE
PRECHARGE
NOP
ACTIVE
NOP
tCMS tCMH
DQM
tAS
Row
Address
tAS
Column m
tAH
All banks
Row
Row
A10
tAS
BA0, BA1
tAH
tAH
Bank
Disable auto precharge
Single bank
Bank
Bank
tDS
DIN
DQ
tRCD
tRP
tWR
tRAS
tRC
Don’t Care
Note:
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Bank
tDH
1. For this example, BL = 1 and the WRITE burst is followed by a manual PRECHARGE.
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AUTO REFRESH Operation
AUTO REFRESH Operation
The AUTO REFRESH command is used during normal operation of the device to refresh
the contents of the array. This command is nonpersistent, so it must be issued each
time a refresh is required. All active banks must be precharged prior to issuing an AUTO
REFRESH command. The AUTO REFRESH command should not be issued until the
minimum tRP is met following the PRECHARGE command. Addressing is generated by
the internal refresh controller. This makes the address bits “Don’t Care” during an AUTO REFRESH command.
After the AUTO REFRESH command is initiated, it must not be interrupted by any executable command until tRFC has been met. During tRFC time, COMMAND INHIBIT or
NOP commands must be issued on each positive edge of the clock. The SDRAM requires that every row be refreshed each tREF period. Providing a distributed AUTO REFRESH command—calculated by dividing the refresh period (tREF) by the number of
rows to be refreshed—meets the timing requirement and ensures that each row is refreshed. Alternatively, to satisfy the refresh requirement a burst refresh can be employed
after every tREF period by issuing consecutive AUTO REFRESH commands for the number of rows to be refreshed at the minimum cycle rate (tRFC).
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AUTO REFRESH Operation
Figure 52: Auto Refresh Mode
T0
CLK
T1
tCK
T2
((
))
((
))
tCH
tCKS
tCKH
tCMS
tCMH
PRECHARGE
NOP
AUTO
REFRESH
NOP
((
))
( ( NOP
))
Address
All banks
A10
Single bank
tAS
AUTO
REFRESH
NOP
((
))
( ( NOP
))
ACTIVE
((
))
((
))
((
))
((
))
((
))
((
))
Row
((
))
((
))
((
))
((
))
Row
((
))
((
))
((
))
((
))
Bank
((
))
((
))
tAH
Bank(s)
DQ High-Z
tRP
tRFC
tRFC
Precharge all
active banks
Note:
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To + 1
((
))
((
))
((
))
DQM
BA0, BA1
((
))
((
))
((
))
CKE
Command
Tn + 1
tCL
Don’t Care
1. Back-to-back AUTO REFRESH commands are not required.
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SELF REFRESH Operation
SELF REFRESH Operation
The self refresh mode can be used to retain data in the device, even when the rest of the
system is powered down. When in self refresh mode, the device retains data without external clocking. The SELF REFRESH command is initiated like an AUTO REFRESH command, except CKE is disabled (LOW). After the SELF REFRESH command is registered,
all the inputs to the device become “Don’t Care” with the exception of CKE, which must
remain LOW.
After self refresh mode is engaged, the device provides its own internal clocking, enabling it to perform its own AUTO REFRESH cycles. The device must remain in self refresh mode for a minimum period equal to tRAS and remains in self refresh mode for an
indefinite period beyond that.
The procedure for exiting self refresh requires a sequence of commands. First, CLK
must be stable prior to CKE going back HIGH. (Stable clock is defined as a signal cycling
within timing constraints specified for the clock ball.) After CKE is HIGH, the device
must have NOP commands issued for a minimum of two clocks for tXSR because time is
required for the completion of any internal refresh in progress.
Upon exiting the self refresh mode, AUTO REFRESH commands must be issued according to the distributed refresh rate (tREF/refresh row count) as both SELF REFRESH and
AUTO REFRESH utilize the row refresh counter.
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SELF REFRESH Operation
Figure 53: Self Refresh Mode
T0
CLK
T1
tCK
tCL
tCH
T2
tCKS
CKE
Command
tCKS
tCKH
tCMS
tCMH
PRECHARGE
((
))
((
))
((
))
NOP
AUTO
REFRESH
((
))
((
))
Tn + 1
((
))
((
))
((
))
))
((
))
((
))
Address
((
))
((
))
((
))
((
))
((
))
((
))
((
))
((
))
((
))
((
))
((
))
((
))
((
))
((
))
Single bank
tAS
BA0, BA1
DQ
tAH
Bank(s)
High-Z
tRP
Precharge all
active banks
tXSR
Enter self refresh mode
Exit self refresh mode
(Restart refresh time base)
CLK stable prior to exiting
self refresh mode
Note:
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AUTO
REFRESH
NOP ( (
((
))
((
))
All banks
To + 2
((
))
((
))
DQM
A10
To + 1
Don’t Care
1. Each AUTO REFRESH command performs a REFRESH cycle. Back-to-back commands are
not required.
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Power-Down
Power-Down
Power-down occurs if CKE is registered LOW coincident with a NOP or COMMAND INHIBIT when no accesses are in progress. If power-down occurs when all banks are idle,
this mode is referred to as precharge power-down; if power-down occurs when there is a
row active in any bank, this mode is referred to as active power-down. Entering powerdown deactivates the input and output buffers, excluding CKE, for maximum power
savings while in standby. The device cannot remain in the power-down state longer
than the refresh period (64ms) because no REFRESH operations are performed in this
mode.
The power-down state is exited by registering a NOP or COMMAND INHIBIT with CKE
HIGH at the desired clock edge (meeting tCKS).
Figure 54: Power-Down Mode
T0
T1
tCK
CLK
T2
((
))
((
))
tCL
tCH
tCKS
CKE
tCKS
Tn + 2
tCKS
((
))
tCKH
tCMS tCMH
Command
Tn + 1
NOP
PRECHARGE
((
))
((
))
NOP
NOP
ACTIVE
DQM
((
))
((
))
Address
((
))
((
))
Row
((
))
((
))
Row
((
))
((
))
Bank
All banks
A10
Single bank
tAS
BA0, BA1
DQ
tAH
Bank(s)
High-Z
((
))
Two clock cycles
Input buffers gated off
All banks idle
while in power-down mode
Precharge all
active banks
All banks idle, enter
power-down mode
Exit power-down mode
Don’t Care
Note:
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1. Violating refresh requirements during power-down may result in a loss of data.
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Clock Suspend
Clock Suspend
The clock suspend mode occurs when a column access/burst is in progress and CKE is
registered LOW. In the clock suspend mode, the internal clock is deactivated, freezing
the synchronous logic.
For each positive clock edge on which CKE is sampled LOW, the next internal positive
clock edge is suspended. Any command or data present on the input balls when an internal clock edge is suspended will be ignored; any data present on the DQ balls remains driven; and burst counters are not incremented, as long as the clock is suspended.
Exit clock suspend mode by registering CKE HIGH; the internal clock and related operation will resume on the subsequent positive clock edge.
Figure 55: Clock Suspend During WRITE Burst
T0
T1
NOP
WRITE
T2
T3
T4
T5
NOP
NOP
DIN
DIN
CLK
CKE
Internal
clock
Command
Address
DIN
Bank,
Col n
DIN
Don’t Care
Note:
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1. For this example, BL = 4 or greater, and DQM is LOW.
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Clock Suspend
Figure 56: Clock Suspend During READ Burst
T0
T1
T2
T3
T4
T5
T6
CLK
CKE
Internal
clock
Command
READ
Address
Bank,
Col n
DQ
NOP
NOP
NOP
DOUT
DOUT
NOP
DOUT
NOP
DOUT
Don’t Care
Note:
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1. For this example, CL = 2, BL = 4 or greater, and DQM is LOW.
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Clock Suspend
Figure 57: Clock Suspend Mode
T0
T1
tCK
CLK
T2
T3
T4
T5
T6
T7
T8
T9
tCL
tCH
tCKS
tCKH
CKE
tCKS tCKH
tCMS
Command
tCMH
READ
NOP
NOP
NOP
NOP
NOP
WRITE
NOP
tCMS tCMH
DQM
tAS
Address
tAH
Column e
Column m
tAS
tAH
tAS
tAH
A10
BA0, BA1
Bank
Bank
tAC
tOH
tAC
DQ
tLZ
tHZ
DOUT
DOUT
tDS
tDH
DIN
DIN
Don’t Care
Note:
Undefined
1. For this example, BL = 2, CL = 3, and auto precharge is disabled.
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Micron and the Micron logo are trademarks of Micron Technology, Inc.
All other trademarks are the property of their respective owners.
This data sheet contains minimum and maximum limits specified over the power supply and temperature range set forth herein.
Although considered final, these specifications are subject to change, as further product development and data characterization sometimes occur.
PDF: 09005aef8091e6d1
256Mb_sdr.pdf - Rev. W 05/15 EN
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Micron Technology, Inc. reserves the right to change products or specifications without notice.
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