HIGH-SPEED 3.3V
32K x 16 BANK-SWITCHABLE
DUAL-PORTED SRAM WITH
EXTERNAL BANK SELECTS
Features
◆
IDT70V7278S/L
◆
◆
◆
◆
32K x 16 Bank-Switchable Dual-Ported SRAM Architecture
– Four independent 8K x 16 banks
– 512 kilobit of memory on chip
Fast asynchronous address-to-data access time: 15ns
User-controlled input pins included for bank selects
Independent port controls with asynchronous address &
data busses
Four 16-bit mailboxes available to each port for inter-
processor communications; interrupt option
◆
◆
◆
◆
◆
◆
Interrupt flags with programmable masking
Dual Chip Enables allow for depth expansion without
external logic
UB
and
LB
are available for x8 or x16 bus matching
LVTTL-compatible, single 3.3V (±5%) power supply
Available in a 100-pin Thin Quad Flatpack
Industrial temperature range (-40° to +85°C) is available
for selected speeds
Functional Block Diagram
MUX
R/W
L
CE
0L
CE
1L
UB
L
LB
L
OE
L
8Kx16
MEMORY
ARRAY
(BANK 0)
MUX
MUX
R/W
R
CE
0R
CE
1R
UB
R
LB
R
OE
R
D
E
D S
N N
E G
M SI
M E
O D
C
E W
R E
T N
O
N
CONTROL
LOGIC
CONTROL
LOGIC
I/O
8L-15L
I/O
0L-7L
I/O
CONTROL
I/O
CONTROL
I/O
8R-15R
I/O
0R-7R
A
12L
A
0L (1)
ADDRESS
DECODE
8Kx16
MEMORY
ARRAY
(BANK 1)
MUX
ADDRESS
DECODE
A
12R
A
0R(1)
BA
1L
BA
0L
BANK
DECODE
BANK
DECODE
BA
1R
BA
0R
MUX
8Kx16
MEMORY
ARRAY
(BANK 3)
MUX
BKSEL
3(2)
BKSEL
0(2)
BANK
SELECT
MBSEL
L
INT
L
A
5L(1)
A
0L(1)
LB
L
/UB
L
OE
L
R/W
L
CE
L
MAILBOX
INTERRUPT
LOGIC
A
5R(1)
A
0R(1)
LB
R
/UB
R
OE
R
R/W
R
CE
R
MBSEL
R
INT
R
R
O
F
,
4078 drw 01
NOTES:
1. The first six address pins for each port serve dual functions. When
MBSEL
= V
IH
, the pins serve as memory address inputs. When
MBSEL
= V
IL
, the pins serve as mailbox
address inputs.
2. Each bank has an input pin assigned that allows the user to toggle the assignment of that bank between the two ports. Refer to Truth Table I for more details.
JUNE 2000
1
©2000 Integrated Device Technology, Inc.
DSC-4078/7
IDT70V7278S/L
32K x 16 3.3V Bank-Switchable Dual-Ported SRAM with External Bank Selects
Industrial and Commercial Temperature Ranges
Description
The IDT70V7278 is a high-speed 32K x 16 (512K bit) Bank-
Switchable Dual-Ported SRAM organized into four independent 8K x
16 banks. The device has two independent ports with separate
controls, addresses, and I/O pins for each port, allowing each port to
asynchronously access any 8K x 16 memory block not already
accessed by the other port. Accesses by the ports into specific banks
are controlled via bank select pin inputs under the user's control.
Mailboxes are provided to allow inter-processor communications.
Interrupts are provided to indicate mailbox writes have occurred. An
automatic power down feature controlled by the chip enables (CE
0
and
CE
1
) permits the on-chip circuitry of each port to enter a very low
standby power mode and allows fast depth expansion.
The IDT70V7278 offers a maximum address-to-data access time
as fast as 15ns, and is packaged in a 100-pin Thin Quad Flatpack
(TQFP).
Functionality
The IDT70V7278 is a high-speed asynchronous 32K x 16 Bank-
Switchable Dual-Ported SRAM, organized in four 8K x 16 banks. The
two ports are permitted independent, simultaneous access into sepa-
rate banks within the shared array. There are four user-controlled
Bank Select input pins, and each of these pins is associated with a
specific bank within the memory array. Access to a specific bank is
gained by placing the associated Bank Select pin in the appropriate
D
E
D S
N N
E G
M SI
M E
O D
C
E W
R E
T N
O
N
state: V
IH
assigns the bank to the left port, and V
IL
assigns the bank to
the right port (See Truth Table IV). Once a bank is assigned to a
particular port, the port has full access to read and write within that
bank. Each port can be assigned as many banks within the array as
needed, up to and including all four banks.
The IDT70V7278 provides mailboxes to allow inter-processor
communications. Each port has four 16-bit mailbox registers available
to which it can write and read and which the opposite port can read
only. These mailboxes are external to the common SRAM array, and
are accessed by setting
MBSEL
= V
IL
while setting
CE
= V
IH
. Each
mailbox has an associated interrupt: a port can generate an interrupt
to the opposite port by writing to the upper byte of any one of its four
16-bit mailboxes. The interrupted port can clear the interrupt by
reading the upper byte. This read will not alter the contents of the
mailbox.
If desired, any source of interrupt can be independently masked via
software. Two registers are provided to permit interpretation of inter-
rupts: the Interrupt Cause Register and the Interrupt Status Register.
The Interrupt Cause Register gives the user a snapshot of what has
caused the interrupt to be generated - the specific mailbox written to.
The information in this register provides post-mask signals: Interrupt
sources that have been masked will not be updated. The Interrupt
Status Register gives the user the status of all bits that could potentially
cause an interrupt regardless of whether they have been masked.
Truth Table V gives a detailed explanation of the use of these registers.
R
O
F
6.42
2
IDT70V7278S/L
32K x 16 3.3V Bank-Switchable Dual-Ported SRAM with External Bank Selects
Industrial and Commercial Temperature Ranges
Pin Configurations
(1,2,3)
INDEX
NOTES:
1. All V
CC
pins must be connected to power supply.
2. All GND pins must be connected to ground supply.
3. Package body is approximately 14mm x 14mm x 1.4mm.
4. This package code is used to reference the package diagram.
5. This text does not indicate orientation of the actual part-marking.
D
E
D S
N N
E G
M SI
M E
O D
C
E W
R E
T N
O
N
14
15
16
17
18
19
20
21
22
23
24
62
61
60
59
58
57
56
55
54
53
52
51
25
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
A
6L
A
7L
A
8L
A
9L
A
10L
A
11L
NC
NC
BKSEL
0
LB
L
UB
L
CE
0L
CE
1L
MBSEL
L
Vcc
R/W
L
OE
L
GND
GND
I/O
15L
I/O
14L
I/O
13L
I/O
12L
I/O
11L
I/O
10L
10099 98 97 96 95 94 93 92 91 90 89 88 87 86 85 84 83 82 81 80 79 78 77 76
75
2
74
3
73
1
4
5
6
7
8
9
10
11
12
13
72
71
70
69
68
67
66
65
64
63
A
5L
A
4L
A
3L
A
2L
A
1L
A
0L
BA
1L
BA
0L
A
12L
NC
BKSEL
1
INT
L
GND
GND
INT
R
BKSEL
2
A
12R
BA
0R
BA
1R
A
0R
A
1R
A
2R
A
3R
A
4R
A
5R
A
6R
A
7R
A
8R
A
9R
A
10R
A
11R
NC
NC
BKSEL
3
LB
R
UB
R
CE
0R
CE
1R
MBSEL
R
GND
R/W
R
OE
R
GND
GND
I/O
15R
I/O
14R
I/O
13R
I/O
12R
I/O
11R
I/O
10R
IDT70V7278PF
PN100-1(4)
100-Pin TQFP
Top View(5)
R
O
F
,
I/O
9L
I/O
8L
Vcc
I/O
7
L
I/O
6L
I/O
5L
I/O
4L
I/O
3L
I/O
2L
GND
I/O1
L
I/O
0L
GND
I/O
0R
I/O
1R
I/O
2R
I/O
3R
I/O
4R
I/O
5R
I/O
6R
Vcc
I/O
7R
I/O
8R
I/O
9R
NC
4078 drw 02
Pin Names
A
0
- A
12
(1,6)
BA
0
- BA
1
(1)
MBSEL
(1)
Address Inputs
Bank Address Inputs
Mailbox Access Control Gate
Bank Select Inputs
Read/Write Enable
Output Enable
Chip Enables
BKSEL
0-3
(2)
R/W
(1)
OE
(1)
CE
0
,
CE
1
(1)
UB, LB
(1)
I/O Byte Enables
I/O
0
- I/O
15
(1)
INT
(1)
V
CC
(4)
Bidirectional Data Input/Output
Interrupt Flag (Output)
(3)
3.3VPower
Ground
4078 tbl 01
GND
(5)
NOTES:
1. Duplicated per port.
2. Each bank has an input pin assigned that allows the user to toggle the assign-
ment of that bank between the two ports. Refer to Truth Table IV for more details.
When changing the bank assignment, accesses of the affected banks must be
suspended. Accesses may continue uninterrupted in banks that are not being
reallocated.
3. Generated upon mailbox access.
4. All Vcc pins must be connected to power supply.
5. All GND pins must be connected to ground supply.
6. The first six address pins (A
0
-A
5
) for each port serve dual functions. When MBSEL
= V
IH
, the pins serve as memory address inputs. When MBSEL = V
IL
, the pins serve
as mailbox address inputs (A
6
-A
12
ignored).
6.42
3
IDT70V7278S/L
32K x 16 3.3V Bank-Switchable Dual-Ported SRAM with External Bank Selects
Industrial and Commercial Temperature Ranges
Truth Table I – Chip Enable
(1,2,3,4)
CE
CE
0
V
IL
L
< 0.2V
V
IH
H
X
>V
CC
-0.2V
X
CE
1
V
IH
>V
CC
-0.2V
X
V
IL
X
<0.2V
Mode
Port Selected (TTL Active)
Port Selected (CMOS Active)
Port Deselected (TTL Inactive)
Port Deselected (TTL Inactive)
Port Deselected (CMOS Inactive)
Port Deselected (CMOS Inactive)
NOTES:
1. Chip Enable references are shown above with the actual
CE
0
and CE
1
levels,
CE
is a reference only.
2. Port "A" and "B" references are located where
CE
is used.
3. "H" = V
IH
and "L" = V
IL
.
4.
CE
and
MBSEL
cannot both be active at the same time.
Truth Table II – Non-Contention Read/Write Control
Inputs
(1)
Outputs
CE
(2)
H
R/W
X
OE
X
UB
X
LB
X
MBSEL
H
I/O
8-15
I/O
0-7
NOTES:
1. BA
0L
- BA
1L
≠
BA
0R
- BA
1R
: cannot access same bank simultaneously from both ports.
2. Refer to Truth Table I.
3.
CE
and
MBSEL
cannot both be active at the same time.
Truth Table III – Mailbox Read/Write Control
(1)
Inputs
CE
(2)
H
H
H
L
R/W
H
H
L
X
OE
L
L
X
X
UB
X
(3)
L
L
(3)
X
LB
X
(3)
L
L
(3)
X
MBSEL
L
L
L
L
I/O
8-15
DATA
OUT
DATA
OUT
DATA
IN
____
D
E
D S
N N
E G
M SI
M E
O D
C
E W
R E
T N
O
N
Mode
High-Z
High-Z
High-Z
Deselected: Power-Down
X
(3)
X
L
X
H
L
H
X
(3)
High-Z
Both Bytes Deselected
L
X
H
L
H
DATA
IN
High-Z
High-Z
Write to Upper Byte Only
Write to Lower Byte Only
Write to Both Bytes
L
L
X
H
L
L
H
DATA
IN
DATA
IN
High-Z
L
L
L
X
L
L
H
DATA
IN
H
H
L
H
DATA
OUT
High-Z
Read Upper Byte Only
Read Lower Byte Only
Read Both Bytes
L
H
L
H
L
H
DATA
OUT
L
H
L
L
H
DATA
OUT
High-Z
DATA
OUT
High-Z
X
(3)
X
H
X
X
X
(3)
Outputs Disabled
R
O
F
4078 tbl 02
4078 tbl 03
Outputs
I/O
0-7
DATA
OUT
DATA
OUT
DATA
IN
____
Mode
Read Data from Mailbox,
↓
clears interrupt
Read Data from Mailbox,
↓
clears interrupt
Write Data into Mailbox
Not Allowed
4078 tbl 04
NOTES:
1. There are four mailbox locations per port written to and read from all the I/O's (I/O
0
-I/O
15
). These four mailboxes are addressed by A
0
-A
5.
Refer to Truth Table V.
2. Refer to Truth Table I.
3. Each mailbox location contains a 16-bit word, controllable in bytes by setting input levels to
UB
and
LB
appropriately.
6.42
4
IDT70V7278S/L
32K x 16 3.3V Bank-Switchable Dual-Ported SRAM with External Bank Selects
Industrial and Commercial Temperature Ranges
Absolute Maximum Ratings
(1)
Symbol
V
TERM
(2)
Rating
Terminal Voltage
with Respect
to GND
Temperature
Under Bias
Storage
Temperature
DC Output
Current
Commercial
& Industrial
-0.5 to +4.6
Unit
V
Maximum Operating Temperature
and Supply Voltage
(1)
Grade
Ambient Temperature
Commercial
0
O
C to +70
O
C
-40
O
C to +85
O
C
0V
0V
3.3V
+
5%
3.3V
+
5%
4078 tbl 06
GND
Vcc
T
BIAS
T
STG
I
OUT
-55 to +125
-65 to +150
50
o
C
C
Industrial
o
NOTES:
1. This is the parameter T
A
. This is the "instant on" case temperature.
mA
4078 tbl 05
NOTES:
1. Stresses greater than those listed under ABSOLUTE MAXIMUM RATINGS 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.
2. V
TERM
must not exceed Vcc + 5% for more than 25% of the cycle time or 10ns
maximum, and is limited to < 20mA for the period of V
TERM
> Vcc + 5%.
Capacitance
(1)
Symbol
C
IN
Parameter
(T
A
= +25°C, f = 1.0MHz) TQFP Package
Conditions
(2)
V
IN
= 3dV
Input Capacitance
9
C
OUT
(3)
NOTES:
1. This parameter is determined by device characterization but is not production
tested.
2. 3dV represents the interpolated capacitance when the input and output signals
switch from 0V to 3V or from 3V to 0V.
3. C
OUT
represents C
I/O
as well.
DC Electrical Characteristics Over the Operating
Temperature and Supply Voltage Range
(V
CC
= 3.3V ± 5%)
70V7278S
Symbol
|I
LI
|
|I
LO
|
V
OL
V
OH
Parameter
Input Leakage Current
(1)
Output Leakage Current
Output Low Voltage
Output High Voltage
Test Conditions
V
CC
= 3.465V, V
IN
= 0V to V
CC
CE
= V
IH
,
MBSEL
= V
IH
, V
OUT
= 0V to V
CC
I
OL
= +4mA
I
OH
= -4mA
Min.
___
D
E
D S
N N
E G
M SI
M E
O D
C
E W
R E
T N
O
N
Symbol
V
CC
Parameter
Min.
Typ.
3.3
0
Supply Voltage
Ground
3.135
0
GND
V
IH
V
IL
Input High Voltage
Input Low Voltage
2.0
____
Recommended DC Operating
Conditions
Max.
3.465
0
R
O
F
Unit
V
V
V
V
4078 tbl 07
V
CC
+5%
(2)
0.8
-0.3
(1)
____
NOTES:
1. V
IL
> -1.5V for pulse width less than 10ns.
2. V
TERM
must not exceed Vcc + 5%.
Max.
Unit
pF
Output Capacitance
V
OUT
= 3dV
10
pF
4078 tbl 08
70V7278L
Max.
5
5
0.4
___
Max.
10
10
0.4
___
Min.
___
Unit
µA
µA
V
V
4078 tbl 09
___
___
___
___
2.4
2.4
NOTE:
1. At Vcc
<
2.0V, input leakages are undefined.
6.42
5
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