3.3 VOLT CMOS SuperSync FIFO™
65,536 x 9
131,072 x 9
.EATURES:
•
•
•
•
•
IDT72V281
IDT72V291
•
•
•
•
•
•
•
•
•
•
•
•
•
Choose among the following memory organizations:
IDT72V281
65,536 x 9
IDT72V291
131,072 x 9
Pin-compatible with the IDT72V261/72V271 SuperSync FIFOs
10ns read/write cycle time (6.5ns access time)
Fixed, low first word data latency time
Auto power down minimizes standby power consumption
Master Reset clears entire FIFO
Partial Reset clears data, but retains programmable
settings
Retransmit operation with fixed, low first word data
latency time
Empty, Full and Half-Full flags signal FIFO status
Programmable Almost-Empty and Almost-Full flags, each flag can
default to one of two preselected offsets
Program partial flags by either serial or parallel means
Select IDT Standard timing (using
EF
and
FF
flags) or First Word
Fall Through timing (using
OR
and
IR
flags)
Output enable puts data outputs into high impedance state
Easily expandable in depth and width
Independent Read and Write clocks (permit reading and writing
simultaneously)
Available in the 64-pin Thin Quad Flat Pack (TQFP) and the 64-pin
Slim Thin Quad Flat Pack (STQFP)
High-performance submicron CMOS technology
Industrial Temperature Range (-40°C to + 85°C) is available
DESCRIPTION:
The IDT72V281/72V291 are exceptionally deep, high speed, CMOS
First-In-First-Out (FIFO) memories with clocked read and write controls.
These FIFOs offer numerous improvements over previous SuperSync
FIFOs, including the following:
•
The limitation of the frequency of one clock input with respect to the other has
been removed. The Frequency Select pin (FS) has been removed, thus
it is no longer necessary to select which of the two clock inputs, RCLK or
WCLK, is running at the higher frequency.
•
The period required by the retransmit operation is now fixed and short.
•
The first word data latency period, from the time the first word is written to an
empty FIFO to the time it can be read, is now fixed and short. (The variable
clock cycle counting delay associated with the latency period found on
previous SuperSync devices has been eliminated on this SuperSync family.)
.UNCTIONAL BLOCK DIAGRAM
WEN
WCLK
D
0
-D
8
LD SEN
INPUT REGISTER
OFFSET REGISTER
FF/IR
PAF
EF/OR
PAE
HF
FWFT/SI
WRITE CONTROL
LOGIC
RAM ARRAY
65,536 x 9
131,072 x 9
FLAG
LOGIC
WRITE POINTER
READ POINTER
OUTPUT REGISTER
MRS
PRS
READ
CONTROL
LOGIC
RT
RESET
LOGIC
RCLK
REN
OE
Q
0
-Q
8
4513 drw 01
SuperSyncFIFO is a trademark and the IDT logo is a registered trademark of Integrated Device Technology, Inc.
COMMERCIAL AND INDUSTRIAL TEMPERATURE RANGE
1
2001
Integrated Device Technology, Inc.
APRIL 2001
DSC-4513/1
IDT72V281/72V291
COCOMMCOMMERCIAL
AND INDUSTRIAL TEMPERATURE RANGE
DESCRIPTION (Continued)
SuperSync FIFOs are particularly appropriate for network, video, telecommu-
nications, data communications and other applications that need to buffer large
amounts of data.
The input port is controlled by a Write Clock (WCLK) input and a Write
Enable (WEN) input. Data is written into the FIFO on every rising edge of
WCLK when
WEN
is asserted. The output port is controlled by a Read
Clock (RCLK) input and Read Enable (REN) input. Data is read from the
FIFO on every rising edge of RCLK when
REN
is asserted. An Output
Enable (OE) input is provided for three-state control of the outputs.
The frequencies of both the RCLK and the WCLK signals may vary from 0
to f
MAX
with complete independence. There are no restrictions on the frequency
of the one clock input with respect to the other.
There are two possible timing modes of operation with these devices:
IDT Standard mode and First Word Fall Through (FWFT) mode.
In
IDT Standard mode,
the first word written to an empty FIFO will not
appear on the data output lines unless a specific read operation is
performed. A read operation, which consists of activating
REN
and
enabling a rising RCLK edge, will shift the word from internal memory to the
data output lines.
PIN CON.IGURATIONS
LD
FWFT/SI
GND
WCLK
PRS
EF/OR
RCLK
REN
RT
FF/IR
PAF
HF
V
CC
PAE
MRS
OE
PIN 1
64 63 62 61 60 59 58 57 56 55 54 53 52 51 50 49
WEN
SEN
DC
(1)
V
CC
V
CC
GND
(2)
GND
(2)
GND
(2)
GND
(2)
GND
(2)
GND
(2)
GND
(2)
GND
(2)
GND
(2)
D8
D7
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 31 32
48
47
46
45
44
43
42
41
40
39
38
37
36
35
34
33
DNC
(3)
DNC
(3)
GND
DNC
(3)
DNC
(3)
V
CC
DNC
(3)
DNC
(3)
DNC
(3)
GND
DNC
(3)
DNC
(3)
Q8
Q7
Q6
GND
GND
Q0
Q1
GND
Q2
D5
D4
D3
D2
D1
D0
Q3
V
CC
Q4
Q5
D6
4513 drw 02
TQFP (PN64-1, order code: PF)
STQFP (PP64-1, order code: TF)
TOP VIEW
NOTES:
1. DC = Don’t Care. Must be tied to GND or V
CC
, cannot be left open.
2. This pin may either be tied to ground or left open.
3. DNC = Do Not Connect.
2
IDT72V281/72V291
COMMERCIAL AND INDUSTRIAL TEMPERATURE RANGE
DESCRIPTION (Continued)
In
FWFT mode,
the first word written to an empty FIFO is clocked directly
to the data output lines after three transitions of the RCLK signal. A
REN
does not have to be asserted for accessing the first word. However,
subsequent words written to the FIFO do require a LOW on
REN
for
access. The state of the FWFT/SI input during Master Reset determines the
timing mode in use.
For applications requiring more data storage capacity than a single FIFO
can provide, the FWFT timing mode permits depth expansion by chaining
FIFOs in series (i.e. the data outputs of one FIFO are connected to the
corresponding data inputs of the next). No external logic is required.
These FIFOs have five flag pins,
EF/OR
(Empty Flag or Output
Ready),
FF/IR
(Full Flag or Input Ready),
HF
(Half-full Flag),
PAE
(Programmable Almost-Empty flag) and
PAF
(Programmable Almost-Full
flag). The
EF
and
FF
functions are selected in IDT Standard mode. The
IR
and
OR
functions are selected in FWFT mode.
HF, PAE
and
PAF
are
always available for use, irrespective of timing mode.
PAE
and
PAF
can be programmed independently to switch at any
point in memory. (See Table 1 and Table 2.) Programmable offsets
determine the flag switching threshold and can be loaded by two methods:
parallel or serial. Two default offset settings are also provided, so that
PAE
can be set to switch at 127 or 1,023 locations from the empty boundary and
the
PAF
threshold can be set at 127 or 1,023 locations from the full
boundary. These choices are made with the
LD
pin during Master Reset.
For serial programming,
SEN
together with
LD
on each rising edge
of WCLK, are used to load the offset registers via the Serial Input (SI). For
parallel programming,
WEN
together with
LD
on each rising edge of
WCLK, are used to load the offset registers via D
n
.
REN
together with
LD
on
each rising edge of RCLK can be used to read the offsets in parallel from Q
n
regardless of whether serial or parallel offset loading has been selected.
During Master Reset (MRS) the following events occur: The read and
write pointers are set to the first location of the FIFO. The FWFT pin selects
IDT Standard mode or FWFT mode. The
LD
pin selects either a partial flag
default setting of 127 with parallel programming or a partial flag default
setting of 1,023 with serial programming. The flags are updated according
to the timing mode and default offsets selected.
The Partial Reset (PRS) also sets the read and write pointers to the first
location of the memory. However, the timing mode, partial flag program-
ming method, and default or programmed offset settings existing before
Partial Reset remain unchanged. The flags are updated according to the
timing mode and offsets in effect.
PRS
is useful for resetting a device in
mid-operation, when reprogramming partial flags would be undesirable.
The Retransmit function allows data to be reread from the FIFO more
than once. A LOW on the
RT
input during a rising RCLK edge initiates a
retransmit operation by setting the read pointer to the first location of the
memory array.
If, at any time, the FIFO is not actively performing an operation, the chip
will automatically power down. Once in the power down state, the standby
supply current consumption is minimized. Initiating any operation (by
activating control inputs) will immediately take the device out of the power
down state.
The IDT72V281/72V291 are fabricated using IDT’s high speed submi-
cron CMOS technology.
PARTIAL RESET (PRS)
WRITE CLOCK (WCLK)
WRITE ENABLE (WEN)
LOAD (LD)
DATA IN (D
0
- D
n
)
SERIAL ENABLE(SEN)
FIRST WORD FALL THROUGH/SERIAL INPUT
(FWFT/SI)
FULL FLAG/INPUT READY (FF/IR)
PROGRAMMABLE ALMOST-FULL (PAF)
MASTER RESET (MRS)
READ CLOCK (RCLK)
READ ENABLE (REN)
OUTPUT ENABLE (OE)
DATA OUT (Q
0
- Q
n
)
IDT
72V281
72V291
RETRANSMIT (RT)
EMPTY FLAG/OUTPUT READY (EF/OR)
PROGRAMMABLE ALMOST-EMPTY (PAE)
HALF-FULL FLAG (HF)
4513 drw 03
Figure 1. Block Diagram of Single 65,536 x 9 and 131,072 x 9 Synchronous FIFO
3
IDT72V281/72V291
COCOMMCOMMERCIAL
AND INDUSTRIAL TEMPERATURE RANGE
PIN DESCRIPTION
Symbol
D
0
–D
8
MRS
Name
Data Inputs
Master Reset
I/O
I
I
Description
Data inputs for a 9-bit bus.
MRS
initializes the read and write pointers to zero and sets the output register to
all zeroes. During Master Reset, the FIFO is configured for either FWFT or IDT
Standard mode, one of two programmable flag default settings, and serial or
parallel programming of the offset settings.
PRS
initializes the read and write pointers to zero and sets the output register to
all zeroes. During Partial Reset, the existing mode (IDT or FWFT), programming
method (serial or parallel), and programmable flag settings are all retained.
RT
asserted on the rising edge of RCLK initializes the READ pointer to zero, sets
the
EF
flag to LOW (OR to HIGH in FWFT mode) temporarily and does not disturb
the write pointer, programming method, existing timing mode or programmable flag
settings.
RT
is useful to reread data from the first physical location of the FIFO.
During Master Reset, selects First Word Fall Through or IDT Standard mode.
After Master Reset, this pin functions as a serial input for loading offset registers
When enabled by
WEN,
the rising edge of WCLK writes data into the FIFO and
offsets into the programmable registers for parallel programming, and when
enabled by
SEN,
the rising edge of WCLK writes one bit of data into the
programmable register for serial programming.
WEN
enables WCLK for writing data into the FIFO memory and offset registers.
When enabled by
REN,
the rising edge of RCLK reads data from the FIFO
memory and offsets from the programmable registers.
REN
enables RCLK for reading data from the FIFO memory and offset registers.
OE
controls the output impedance of Q
n.
SEN
enables serial loading of programmable flag offsets.
During Master Reset,
LD
selects one of two partial flag default offsets (127 or 1,023
and determines the flag offset programming method, serial or parallel. After
Master Reset, this pin enables writing to and reading from the offset registers.
This pin must be tied to either V
CC
or GND and must not toggle after Master
Reset.
In the IDT Standard mode, the
FF
function is selected.
FF
indicates whether or
not the FIFO memory is full. In the FWFT mode, the
IR
function is selected.
IR
indicates whether or not there is space available for writing to the FIFO memory.
In the IDT Standard mode, the
EF
function is selected.
EF
indicates whether or
not the FIFO memory is empty. In FWFT mode, the
OR
function is selected.
OR
indicates whether or not there is valid data available at the outputs.
PAF
goes LOW if the number of words in the FIFO memory is more than
total word capacity of the FIFO minus the full offset value m, which is stored in the
Full Offset register. There are two possible default values for m: 127 or 1,023.
PAE
goes LOW if the number of words in the FIFO memory is less than offset n,
which is stored in the Empty Offset register. There are two possible default values
for n: 127 or 1,023. Other values for n can be programmed into the device.
HF
indicates whether the FIFO memory is more or less than half-full.
Data outputs for a 9-bus.
+3.3 Volt power supply pins.
Ground pins.
PRS
Partial Reset
I
RT
Retransmit
I
FWFT/SI
WCLK
First Word Fall
Through/Serial In
Write Clock
I
I
WEN
RCLK
REN
OE
SEN
LD
Write Enable
Read Clock
Read Enable
Output Enable
Serial Enable
Load
I
I
I
I
I
I
DC
FF/IR
Don't Care
Full Flag/
Input Ready
Empty Flag/
Output Ready
Programmable
Almost-Full Flag
Programmable
Almost-Empty Flag
Half-Full Flag
Data Outputs
Power
Ground
I
O
EF/OR
O
PAF
O
PAE
O
HF
Q
0
–Q
8
V
CC
GND
O
O
4
IDT72V281/72V291
COMMERCIAL AND INDUSTRIAL TEMPERATURE RANGE
ABSOLUTE MAXIMUM RATINGS
Symbol
V
TERM
T
STG
I
OUT
Rating
Terminal Voltage
with respect to GND
Storage
Temperature
DC Output Current
Commercial
–0.5 to +4.6
–55 to +125
–50 to +50
Unit
V
°C
mA
RECOMMENDED DC OPERATING
CONDITIONS
Symbol
V
CC
GND
V
IH
V
IL(1)
T
A
T
A
Parameter
Supply Voltage(Com’l & Ind’’l)
Supply Voltage(Com’l & Ind’l)
Input High Voltage
(Com’l & Ind’l)
Input Low Voltage
(Com’l & Ind’l)
Operating Temperature
Commercial
Operating Temperature
Industrial
Min.
3.0
0
2.0
—
0
-40
Typ.
3.3
0
—
—
—
Max.
3.6
0
V
CC
+ 0.5
0.8
70
85
Unit
V
V
V
V
O
NOTE:
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.
C
°C
NOTE:
1. 1.5V undershoots are allowed for 10ns once per cycle.
DC ELECTRICAL CHARACTERISTICS
(Commercial: V
CC
= 3.3V ± 0.3V, T
A
= 0
o
C to +70
o
C; Industrial: V
CC =
3.3V
±
0.3V, TA= -40°C to +85°C)
IDT72V281L
IDT72V291L
Com’l & Ind’l
(1)
t
CLK
= 10, 15, 20 ns
Symbol
I
LI
(2)
I
LO
(3)
V
OH
V
OL
I
CC1
(4,5,6)
I
CC2
(4,7)
NOTES
:
2.
3.
4.
5.
6.
Parameter
Input Leakage Current
Output Leakage Current
Output Logic “1” Voltage, I
OH
= –2 mA
Output Logic “0” Voltage, I
OL
= 8 mA
Active Power Supply Current
Standby Current
Min.
–1
–10
2.4
—
—
—
Max.
1
10
—
0.4
55
20
Unit
µA
µA
V
V
mA
mA
Measurements with 0.4
≤
V
IN
≤
V
CC
.
OE
≥
V
IH,
0.4
≤
V
OUT
≤
V
CC.
Tested with outputs open (I
OUT
= 0).
RCLK and WCLK toggle at 20 MHz and data inputs switch at 10 MHz.
Typical I
CC1
= 11 + 1.65*f
S
+ 0.02*C
L
*f
S
(in mA) with V
CC
= 3.3V, t
A
= 25
o
C, f
S
= WCLK frequency = RCLK frequency (in MHz, using TTL levels), data switching at f
S
/2, C
L
= capacitive load (in pF).
7. All Inputs = V
CC
- 0.2V or GND + 0.2V, except RCLK and WCLK, which toggle at 20 MHz.
1.
Industrial temperature range product for the 15ns speed grade is available as a standard device.
CAPACITANCE
(T
A
= +25
o
C, f = 1.0MHz)
Symbol
C
IN
(2)
C
OUT
(1,2)
Parameter
(1)
Input
Capacitance
Output
Capacitance
Conditions
V
IN
= 0V
V
OUT
= 0V
Max.
10
10
Unit
pF
pF
NOTES:
1. With output deselected, (OE
≥
V
IH
).
2. Characterized values, not currently tested.
5
