ADVANCE
4Mb: 256K x 18, 128K x 32/36
FLOW-THROUGH ZBT SRAM
4Mb
®
ZBT SRAM
FEATURES
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
High frequency and 100 percent bus utilization
Fast cycle times: 10ns, 11ns and 12ns
Single +3.3V
±5%
power supply (V
DD
)
Separate +3.3V or +2.5V isolated output buffer supply
(V
DD
Q)
Advanced control logic for minimum control signal
interface
Individual BYTE WRITE controls may be tied LOW
Single R/W# (read/write) control pin
CKE# pin to enable clock and suspend operations
Three chip enables for simple depth expansion
Clock-controlled and registered addresses, data I/Os
and control signals
Internally self-timed, fully coherent WRITE
Internally self-timed, registered outputs to eliminate
the need to control OE#
SNOOZE MODE for reduced-power standby
Common data inputs and data outputs
Linear or Interleaved Burst Modes
Burst feature (optional)
Pin/function compatibility with 2Mb, 8Mb and 16Mb
ZBT SRAM
Automatic power-down
MT55L256L18F, MT55L128L32F,
MT55L128L36F; MT55L256V18F,
MT55L128V32F, MT55L128V36F
3.3V V
DD
, 3.3V or 2.5V I/O
100-Pin TQFP*
(D-1)
*JEDEC-standard MS-026 BHA (LQFP).
GENERAL DESCRIPTION
The Micron
®
Zero Bus Turnaround
™
(ZBT
®
) SRAM family
employs high-speed, low-power CMOS designs using an
advanced CMOS process.
Micron’s 4Mb ZBT SRAMs integrate a 256K x 18,
128K x 32, or 128K x 36 SRAM core with advanced
synchronous peripheral circuitry and a 2-bit burst counter.
These SRAMs are optimized for 100 percent bus utilization,
eliminating any turnaround cycles for READ to WRITE, or
WRITE to READ, transitions. All synchronous inputs pass
through registers controlled by a positive-edge-triggered
single clock input (CLK). The synchronous inputs include
all addresses, all data inputs, chip enable (CE#), two
additional chip enables for easy depth expansion (CE2,
CE2#), cycle start input (ADV/LD#), synchronous clock
enable (CKE#), byte write enables (BWa#, BWb#, BWc#
and BWd#) and read/write (R/W#).
Asynchronous inputs include the output enable (OE#,
which may be tied LOW for control signal minimization),
clock (CLK) and snooze enable (ZZ, which may be tied
LOW if unused). There is also a burst mode pin (MODE)
that selects between interleaved and linear burst modes.
MODE may be tied HIGH, LOW or left unconnected if burst
is unused. The flow-through data-out (Q) is enabled by
OE#. WRITE cycles can be from one to four bytes wide as
controlled by the write control inputs.
OPTIONS
• Timing (Access/Cycle/MHz)
7.5ns/10ns/100 MHz
8.5ns/11ns/90 MHz
9ns/12ns/83 MHz
• Configurations
3.3V I/O
256K x 18
128K x 32
128K x 36
2.5V I/O
256K x 18
128K x 32
128K x 36
• Package
100-pin TQFP
MARKING
-10
-11
-12
MT55L256L18F
MT55L128L32F
MT55L128L36F
MT55L256V18F
MT55L128V32F
MT55L128V36F
T
• Part Number Example: MT55L256L18FT-11
4Mb: 256K x 18, 128K x 32/36 Flow-Through ZBT SRAM
MT55L256L18F.p65 – Rev. 9/99
1
Micron Technology, Inc., reserves the right to change products or specifications without notice.
©1999,
Micron Technology, Inc.
ADVANCE
4Mb: 256K x 18, 128K x 32/36
FLOW-THROUGH ZBT SRAM
FUNCTIONAL BLOCK DIAGRAM
256K x 18
18
SA0, SA1, SA
MODE
CLK
CKE#
K
CE
ADV/LD#
K
WRITE ADDRESS
REGISTER
ADDRESS
REGISTER
18
SA1
D1
SA0
D0
16
Q1 SA1'
SA0'
Q0
18
18
O
U
T
P
U
T
B
U
F
F
E
R
S
E
18
BURST
LOGIC
ADV/LD#
BWa#
BWb#
R/W#
WRITE REGISTRY
AND DATA COHERENCY
CONTROL LOGIC
WRITE
DRIVERS
256K x 9 x 2
MEMORY
ARRAY
S
E
N
S
E
A
M
P
S
D
A
T
A
S
T
E
E
R
I
N
G
DQs
OE#
CE#
CE2
CE2#
READ LOGIC
INPUT
E
REGISTER
FUNCTIONAL BLOCK DIAGRAM
128K x 32/36
17
SA0, SA1, SA
MODE
CLK
CKE#
K
CE
ADV/LD#
K
WRITE ADDRESS
REGISTER
ADDRESS
REGISTER
17
SA1
D1
SA0
D0
15
Q1 SA1'
SA0'
Q0
17
17
O
U
T
P
U
T
B
U
F
F
E
R
S
E
17
BURST
LOGIC
ADV/LD#
BWa#
BWb#
BWc#
BWd#
R/W#
WRITE REGISTRY
AND DATA COHERENCY
CONTROL LOGIC
WRITE
DRIVERS
128K x 8 x 4
(x32)
128K x 9 x 4
(x36)
MEMORY
ARRAY
S
E
N
S
E
A
M
P
S
D
A
T
A
S
T
E
E
R
I
N
G
DQs
OE#
CE#
CE2
CE2#
INPUT
E
REGISTER
READ LOGIC
NOTE:
Functional Block Diagrams illustrate simplified device operation. See Truth Table, Pin Descriptions and timing
diagrams for detailed information.
4Mb: 256K x 18, 128K x 32/36 Flow-Through ZBT SRAM
MT55L256L18F.p65 – Rev. 9/99
2
Micron Technology, Inc., reserves the right to change products or specifications without notice.
©1999,
Micron Technology, Inc.
ADVANCE
4Mb: 256K x 18, 128K x 32/36
FLOW-THROUGH ZBT SRAM
GENERAL DESCRIPTION (continued)
All READ, WRITE and DESELECT cycles are initiated by
the ADV/LD# input. Subsequent burst addresses can be
internally generated as controlled by the burst advance pin
(ADV/LD#). Use of burst mode is optional. It is allowable
to give an address for each individual READ and WRITE
cycle. BURST cycles wrap around after the fourth access
from a base address.
To allow for continuous, 100 percent use of the data bus,
the flow-through ZBT SRAM uses a LATE WRITE cycle. For
example, if a WRITE cycle begins in clock cycle one, the
address is present on rising edge one. BYTE WRITEs need
to be asserted on the same cycle as the address. The write
data associated with the address is required one cycle later,
or on the rising edge of clock cycle two.
Address and write control are registered on-chip to sim-
plify WRITE cycles. This allows self-timed WRITE cycles.
Individual byte enables allow individual bytes to be writ-
ten. During a BYTE WRITE cycle, BWa# controls DQa pins;
BWb# controls DQb pins; BWc# controls DQc pins; and
BWd# controls DQd pins. Cycle types can only be defined
when an address is loaded, i.e., when ADV/LD# is LOW.
Parity/ECC bits are only available on the x18 and x36
versions.
Micron’s 4Mb ZBT SRAMs operate from a +3.3V V
DD
power supply, and all inputs and outputs are LVTTL-
compatible. Users can choose either a 2.5V or 3.3V I/O
version. The device is ideally suited for systems requiring
high bandwidth and zero bus turnaround delays.
Please refer to the Micron Web site (www.micron.com/
mti/msp/html/sramprod.html)
for the latest data sheet.
PIN ASSIGNMENT TABLE
PIN #
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
x18
NC
NC
NC
x32
NC
DQc
DQc
V
DD
Q
V
SS
DQc
DQc
DQc
DQc
V
SS
V
DD
Q
DQc
DQc
V
SS
V
DD
V
DD
V
SS
DQd
DQd
V
DD
Q
V
SS
DQd
DQd
DQd
DQd
x36
DQc
DQc
DQc
PIN #
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
x18
x32
x36
V
SS
V
DD
Q
NC
DQd
DQd
NC
DQd
DQd
NC
NC
DQd
MODE (LBO#)
SA
SA
SA
SA
SA1
SA0
DNU
DNU
V
SS
V
DD
DNU
DNU
SA
SA
SA
SA
SA
SA
SA
PIN #
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
x18
NC
NC
NC
x32
NC
DQa
DQa
V
DD
Q
V
SS
DQa
DQa
DQa
DQa
V
SS
V
DD
Q
DQa
DQa
ZZ
V
DD
V
SS
V
SS
DQb
DQb
V
DD
Q
V
SS
DQb
DQb
DQb
DQb
x36
DQa
DQa
DQa
PIN #
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
x18
x32
V
SS
V
DD
Q
DQb
DQb
NC
SA
SA
NF*
NF*
ADV/LD#
OE# (G#)
CKE#
R/W#
CLK
V
SS
V
DD
CE2#
BWa#
BWb#
BWc#
BWd#
CE2
CE#
SA
SA
x36
NC
NC
SA
DQb
DQb
DQb
NC
NC
DQb
DQb
DQc
DQc
DQc
DQc
NC
NC
DQa
DQa
DQb
DQb
DQc
DQc
DQb
DQb
DQd
DQd
DQa
DQa
DQb
DQb
NC
NC
BWc#
BWd#
DQb
DQb
DQb
NC
DQd
DQd
DQd
DQd
DQa
DQa
DQa
NC
DQb
DQb
DQb
DQb
* Pins 83 and 84 are reserved for address expansion.
4Mb: 256K x 18, 128K x 32/36 Flow-Through ZBT SRAM
MT55L256L18F.p65 – Rev. 9/99
3
Micron Technology, Inc., reserves the right to change products or specifications without notice.
©1999,
Micron Technology, Inc.
ADVANCE
4Mb: 256K x 18, 128K x 32/36
FLOW-THROUGH ZBT SRAM
PIN ASSIGNMENT (Top View)
100-Pin TQFP
(D-1)
SA
NC
NC
V
DD
Q
V
SS
NC
DQa
DQa
DQa
V
SS
V
DD
Q
DQa
DQa
V
SS
V
SS
V
DD
ZZ
DQa
DQa
V
DD
Q
V
SS
DQa
DQa
NC
NC
V
SS
V
DD
Q
NC
NC
NC
SA
SA
NF**
NF**
ADV/LD#
OE# (G#)
CKE#
R/W#
CLK
V
SS
V
DD
CE2#
BWa#
BWb#
NC
NC
CE2
CE#
SA
SA
80 79 78 77 76 75 74 73 72 71 70 69 68 67 66 65 64 63 62 61 60 59 58 57 56 55 54 53 52 51
50
81
49
82
48
83
47
84
46
85
45
86
44
87
43
88
42
89
41
90
40
91
39
92
38
93
37
94
36
95
35
96
34
97
33
98
32
99
31
100
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 28 29 30
x18
SA
SA
SA
SA
SA
SA
SA
DNU
DNU
V
DD
V
SS
DNU
DNU
SA0
SA1
SA
SA
SA
SA
MODE
(LBO#)
SA
SA
NF**
NF**
ADV/LD#
OE# (G#)
CKE#
R/W#
CLK
V
SS
V
DD
CE2#
BWa#
BWb#
BWc#
BWd#
CE2
CE#
SA
SA
80 79 78 77 76 75 74 73 72 71 70 69 68 67 66 65 64 63 62 61 60 59 58 57 56 55 54 53 52 51
50
81
49
82
48
83
47
84
46
85
45
86
44
87
43
88
42
89
41
90
40
91
39
92
38
93
37
94
36
95
35
96
34
97
33
98
32
99
31
100
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 28 29 30
NC/DQb*
DQb
DQb
V
DD
Q
V
SS
DQb
DQb
DQb
DQb
V
SS
V
DD
Q
DQb
DQb
V
SS
V
SS
V
DD
ZZ
DQa
DQa
V
DD
Q
V
SS
DQa
DQa
DQa
DQa
V
SS
V
DD
Q
DQa
DQa
NC/DQa*
NC
NC
NC
V
DD
Q
V
SS
NC
NC
DQb
DQb
V
SS
V
DD
Q
DQb
DQb
V
SS
V
DD
V
DD
V
SS
DQb
DQb
V
DD
Q
V
SS
DQb
DQb
DQb
NC
V
SS
V
DD
Q
NC
NC
NC
x32/x36
SA
SA
SA
SA
SA
SA
SA
DNU
DNU
V
DD
V
SS
DNU
DNU
SA0
SA1
SA
SA
SA
SA
MODE
(LBO#)
* NC for x32 version, DQx for x36 version.
** Pins 83 and 84 are reserved for address expansion.
4Mb: 256K x 18, 128K x 32/36 Flow-Through ZBT SRAM
MT55L256L18F.p65 – Rev. 9/99
NC/DQc*
DQc
DQc
V
DD
Q
V
SS
DQc
DQc
DQc
DQc
V
SS
V
DD
Q
DQc
DQc
V
SS
V
DD
V
DD
V
SS
DQd
DQd
V
DD
Q
V
SS
DQd
DQd
DQd
DQd
V
SS
V
DD
Q
DQd
DQd
NC/DQd*
4
Micron Technology, Inc., reserves the right to change products or specifications without notice.
©1999,
Micron Technology, Inc.
ADVANCE
4Mb: 256K x 18, 128K x 32/36
FLOW-THROUGH ZBT SRAM
PIN DESCRIPTIONS
TQFP (x18)
37
36
32-35, 44-50,
80-82, 99, 100
TQFP (x32/x36)
37
36
32-35, 44-50,
81, 82, 99, 100
SYMBOL
SA0
SA1
SA
TYPE
Input
DESCRIPTION
Synchronous Address Inputs: These inputs are registered
and must meet the setup and hold times around the rising
edge of CLK. Pins 83 and 84 are reserved as address
bits for the higher-density 8Mb and 16Mb ZBT SRAMs,
respectively. SA0 and SA1 are the two least significant bits
(LSB) of the address field and set the internal burst counter
if burst is desired.
Synchronous Byte Write Enables: These active LOW
inputs allow individual bytes to be written when a WRITE
cycle is active and must meet the setup and hold times
around the rising edge of CLK. BYTE WRITEs need to be
asserted on the same cycle as the address. BWa# controls
DQa pins; BWb# controls DQb pins; BWc# controls DQc
pins; BWd# controls DQd pins.
Clock: This signal registers the address, data, chip enables,
byte write enables and burst control inputs on its rising
edge. All synchronous inputs must meet setup and hold
times around the clock’s rising edge.
Synchronous Chip Enable: This active LOW input is used to
enable the device and is sampled only when a new external
address is loaded (ADV/LD# LOW).
Synchronous Chip Enable: This active LOW input is used to
enable the device and is sampled only when a new external
address is loaded (ADV/LD# LOW). This input can be used
for memory depth expansion.
Synchronous Chip Enable: This active HIGH input is used
to enable the device and is sampled only when a new
external address is loaded (ADV/LD# LOW). This input can
be used for memory depth expansion.
Output Enable: This active LOW, asynchronous input
enables the data I/O output drivers. G# is the JEDEC-
standard term for OE#.
Synchronous Address Advance/Load: When HIGH, this
input is used to advance the internal burst counter,
controlling burst access after the external address is loaded.
When ADV/LD# is HIGH, R/W# is ignored. A LOW on ADV/
LD# clocks a new address at the CLK rising edge.
Synchronous Clock Enable: This active LOW input permits
CLK to propagate throughout the device. When CKE is
HIGH, the device ignores the CLK input and effectively
internally extends the previous CLK cycle. This input must
meet setup and hold times around the rising edge of CLK.
Snooze Enable: This active HIGH, asynchronous input
causes the device to enter a low-power standby mode in
which all data in the memory array is retained. When ZZ is
active, all other inputs are ignored.
93
94
–
–
93
94
95
96
BWa#
BWb#
BWc#
BWd#
Input
89
89
CLK
Input
98
98
CE#
Input
92
92
CE2#
Input
97
97
CE2
Input
86
86
OE#
(G#)
Input
85
85
ADV/LD# Input
87
87
CKE#
Input
64
64
ZZ
Input
4Mb: 256K x 18, 128K x 32/36 Flow-Through ZBT SRAM
MT55L256L18F.p65 – Rev. 9/99
5
Micron Technology, Inc., reserves the right to change products or specifications without notice.
©1999,
Micron Technology, Inc.
