PRELIMINARY
4Mb: 256K x 18, 128K x 32/36
PIPELINED ZBT SRAM
4Mb ZBT
™
SRAM
WITH S
MART
ZBT OPTION
FEATURES
• S
MART
ZBT™ option to minimize potential bus
contention
• High frequency and 100 percent bus utilization
• Fast cycle times: 6ns, 7.5ns and 10ns
• 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 family
• Automatic power-down
MT55L256L18P1, MT55L256V18P1,
MT55L128L32P1, MT55L128V32P1,
MT55L128L36P1, MT55L128V36P1
3.3V V
DD
, 3.3V or 2.5V I/O
100-Pin TQFP**
119-Pin BGA
OPTIONS
• Timing (Access/Cycle/MHz)
4ns/6ns/166 MHz
4.2ns/7.5ns/133 MHz
5ns/10ns/100 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
119-pin, 14mm x 22mm BGA
*S
MART
ZBT option available.
Part Number Example:
MARKING
-6
-7.5*
-10*
**JEDEC-standard MS-026 BHA (LQFP).
MT55L256L18P1
MT55L128L32P1
MT55L128L36P1
MT55L256V18P1
MT55L128V32P1
MT55L128V36P1
T
B
GENERAL DESCRIPTION
The Micron
®
Zero Bus Turnaround
™
(ZBT
™
) SRAM
family employs high-speed, low-power CMOS designs
using an advanced CMOS process.
The S
MART
ZBT feature enhances the ability of the
SRAM to run in systems with minimal transition time
on the data bus, whether using multiple SRAMs or
complementing ASIC designs.
Micron’s S
MART
ZBT feature allows the
t
KHQX1 (clock
HIGH to output valid) to adapt to the system clock, thus
reducing contention issues. The S
MART
ZBT will drive
the bus turn-on later than the traditional ZBT.
MT55L256L18P1T-10A
4Mb: 256K x 18, 128K x 32/36 Pipelined ZBT SRAM
MT55L256L18P1.p65 – Rev. 3/00
1
Micron Technology, Inc., reserves the right to change products or specifications without notice.
©2000, Micron Technology, Inc.
PRELIMINARY
4Mb: 256K x 18, 128K x 32/36
PIPELINED ZBT SRAM
FUNCTIONAL BLOCK DIAGRAM
256K x 18
18
SA0, SA1, SA
MODE
CLK
CKE#
K
ADDRESS
REGISTER 0
18
16
SA1
SA1'
D1
Q1
SA0
SA0'
BURST
D0
Q0
LOGIC
18
ADV/LD#
K
WRITE ADDRESS
REGISTER 1
WRITE ADDRESS
REGISTER 2
18
18
ADV/LD#
BWa#
BWb#
R/W#
WRITE REGISTRY
AND DATA COHERENCY
CONTROL LOGIC
256K x 9 x 2
WRITE
DRIVERS
MEMORY
ARRAY
S
E
N
S
E
A
M
P
S
O
U
T
P
U
T
R
E
G
I
S
T
E
R
S
D
A
T
A
S
T
E
E
R
I
N
G
O
U
T
P
U
T
B
U
F
F
E
R
S
DQs
E
E
INPUT
REGISTER 1
E
INPUT
REGISTER 0
E
OE#
CE#
CE2
CE2#
READ LOGIC
FUNCTIONAL BLOCK DIAGRAM
128K x 32/36
17
SA0, SA1, SA
MODE
CLK
CKE#
K
ADDRESS
REGISTER 0
17
15
SA1
SA1'
D1
Q1
SA0
SA0'
BURST
D0
Q0
LOGIC
17
ADV/LD#
K
WRITE ADDRESS
REGISTER 1
WRITE ADDRESS
REGISTER 2
17
17
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
O
U
T
P
U
T
R
E
G
I
S
T
E
R
S
D
A
T
A
S
T
E
E
R
I
N
G
O
U
T
P
U
T
B
U
F
F
E
R
S
DQs
E
E
INPUT
REGISTER 1
E
INPUT
REGISTER 0
E
OE#
CE#
CE2
CE2#
READ LOGIC
NOTE:
Functional block diagrams illustrate simplified device operation. See truth tables, pin descriptions and timing diagrams
for detailed information.
4Mb: 256K x 18, 128K x 32/36 Pipelined ZBT SRAM
MT55L256L18P1.p65 – Rev. 3/00
2
Micron Technology, Inc., reserves the right to change products or specifications without notice.
©2000, Micron Technology, Inc.
PRELIMINARY
4Mb: 256K x 18, 128K x 32/36
PIPELINED ZBT SRAM
GENERAL DESCRIPTION (continued)
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 when
transitioning from READ to WRITE, or vice versa. 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 mini-
mization), 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 data-out (Q), en-
abled by OE#, is registered by the rising edge of CLK.
WRITE cycles can be from one to four bytes wide as
controlled by the write control inputs.
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 ad-
vance 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 pipelined ZBT SRAM uses a LATE 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 data associated with the address is
required two cycles later, or on the rising edge of clock
cycle three.
Address and write control are registered on-chip to
simplify WRITE cycles. This allows self-timed WRITE
cycles. Individual byte enables allow individual bytes
to be written. 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 requir-
ing high bandwidth and zero bus turnaround delays.
Please refer to Micron’s Web site (www.micron.com/
mti/msp/html/sramprod.html) for the latest data sheet.
4Mb: 256K x 18, 128K x 32/36 Pipelined ZBT SRAM
MT55L256L18P1.p65 – Rev. 3/00
3
Micron Technology, Inc., reserves the right to change products or specifications without notice.
©2000, Micron Technology, Inc.
PRELIMINARY
4Mb: 256K x 18, 128K x 32/36
PIPELINED ZBT SRAM
TQFP 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
MS#
V
DD
V
DD
V
SS
DQd
DQd
V
DD
Q
V
SS
DQd
DQd
DQd
DQd
x36
DQc
DQc
DQc
PIN # x18
x32
x36
26
V
SS
27
V
DD
Q
28
NC
DQd DQd
29
NC
DQd DQd
30
NC
NC
DQd
31
MODE (LBO#)
32
SA
33
SA
34
SA
35
SA
36
SA1
37
SA0
38
DNU
39
DNU
40
V
SS
41
V
DD
42
DNU
43
DNU
44
SA
45
SA
46
SA
47
SA
48
SA
49
SA
50
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
DD
V
SS
DQb
DQb
V
DD
Q
V
SS
DQb
DQb
DQb
DQb
x36
DQa
DQa
DQa
PIN # x18
x32
x36
76
V
SS
77
V
DD
Q
78
NC
DQb DQb
79
NC
DQb DQb
80
SA
NC
DQb
81
SA
82
SA
83
NF*
84
NF*
85
ADV/LD#
86
OE# (G#)
87
CKE#
88
R/W#
89
CLK
90
V
SS
91
V
DD
92
CE2#
93
BWa#
94
BWb#
95
NC BWc# BWc#
96
NC BWd# BWd#
97
CE2
98
CE#
99
SA
100
SA
NC
NC
DQb
DQb
DQc
DQc
DQc
DQc
NC
NC
DQa
DQa
DQb
DQb
DQc
DQc
DQb
DQb
DQd
DQd
DQa
DQa
DQb
DQb
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, 8Mb and 16Mb respectively.
4Mb: 256K x 18, 128K x 32/36 Pipelined ZBT SRAM
MT55L256L18P1.p65 – Rev. 3/00
4
Micron Technology, Inc., reserves the right to change products or specifications without notice.
©2000, Micron Technology, Inc.
PRELIMINARY
4Mb: 256K x 18, 128K x 32/36
PIPELINED ZBT SRAM
PIN ASSIGNMENT (TOP VIEW)
100-PIN TQFP
SA
NC
NC
V
DD
Q
V
SS
NC
DQa
DQa
DQa
V
SS
V
DD
Q
DQa
DQa
V
SS
V
DD
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
DD
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
MS#
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#)
*No Connect (NC) is used on the x32 version. Parity (DQPx) is used on the x36 version.
**Pins 83 and 84 are reserved for address expansion, 8Mb and 16Mb respectively.
4Mb: 256K x 18, 128K x 32/36 Pipelined ZBT SRAM
MT55L256L18P1.p65 – Rev. 3/00
NC/DQc*
DQc
DQc
V
DD
Q
V
SS
DQc
DQc
DQc
DQc
V
SS
V
DD
Q
DQc
DQc
MS#
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*
5
Micron Technology, Inc., reserves the right to change products or specifications without notice.
©2000, Micron Technology, Inc.
