3.3 VOLT CMOS SuperSync FIFO™
8,192 x 18
16,384 x 18
FEATURES:
•
•
•
•
•
•
•
IDT72V255LA
IDT72V265LA
•
•
•
•
•
•
•
•
•
•
•
•
•
Choose among the following memory organizations:
IDT72V255LA
8,192 x 18
IDT72V265LA
16,384 x 18
Pin-compatible with the IDT72V275/72V285 and IDT72V295/
72V2105 SuperSync FIFOs
Functionally compatible with the 5 Volt IDT72255/72265 family
10ns read/write cycle time (6.5ns access time)
Fixed, low first word data latency time
5V input tolerant
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 IDT72V255LA/72V265LA are functionally compatible versions of the
IDT72255/72265 designed to run off a 3.3V supply for very low power
consumption. The IDT72V255LA/72V265LA 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.
FUNCTIONAL BLOCK DIAGRAM
WEN
WCLK
D
0
-D
17
LD SEN
INPUT REGISTER
OFFSET REGISTER
FF/IR
PAF
EF/OR
PAE
HF
FWFT/SI
WRITE CONTROL
LOGIC
RAM ARRAY
8,192 x 18
16,384 x 18
FLAG
LOGIC
WRITE POINTER
READ POINTER
READ
CONTROL
LOGIC
OUTPUT REGISTER
MRS
PRS
RT
RESET
LOGIC
RCLK
REN
OE
Q
0
-Q
17
4672 drw 01
The IDT logo is a registered trademark and the SuperSyncFIFO is a trademark of Integrated Device Technology, Inc.
COMMERCIAL AND INDUSTRIAL TEMPERATURE RANGES
1
©
2001 Integrated Device Technology, Inc
APRIL 2001
DSC-4672/1
IDT72V255LA/72V265LA 3.3 VOLT CMOS SuperSync FIFO™
8,192 x 18, 16,384 x 18
COMMERCIAL AND INDUSTRIAL
TEMPERATURE RANGES
DESCRIPTION (CONTINUED)
•
•
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.)
SuperSync FIFOs are particularly appropriate for networking, video,
telecommunications, 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 fMAX with complete independence. There are no restrictions on the
frequency of one clock input with respect to the other.
PIN CONFIGURATIONS
WCLK
PRS
LD
FWFT/SI
GND
EF/OR
RCLK
REN
RT
OE
FF/IR
MRS
PAF
HF
V
CC
PAE
PIN 1
64 63 62 61 60 59 58 57 56 55 54 53 52 51 50 49
WEN
SEN
DC
(1)
V
CC
GND
D17
D16
D15
D14
D13
D12
D11
D10
D9
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
Q17
Q16
GND
Q15
Q14
V
CC
Q13
Q12
Q11
GND
Q10
Q9
Q8
Q7
Q6
GND
GND
Q0
Q1
GND
Q2
Q3
V
CC
Q4
Q5
D1
D0
D5
D4
D3
D2
D6
4672 drw 02
TQFP (PN64-1, ORDER CODE: PF)
STQFP (PP64-1, ORDER CODE: TF)
TOP VIEW
NOTE:
1. DC = Don’t Care. Must be tied to GND or V
CC
, cannot be left open.
2
IDT72V255LA/72V265LA 3.3 VOLT CMOS SuperSync FIFO™
8,192 x 18, 16,384 x 18
COMMERCIAL AND INDUSTRIAL
TEMPERATURE RANGES
DESCRIPTION (CONTINUED)
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.
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 I and Table II.) 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 Dn.
REN
together with
LD
on each rising edge
of RCLK can be used to read the offsets in parallel from Qn 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 programming
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 IDT72V255LA/72V265LA are fabricated using IDT’s high speed
submicron 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
72V255LA
72V265LA
RETRANSMIT (RT)
EMPTY FLAG/OUTPUT READY (EF/OR)
PROGRAMMABLE ALMOST-EMPTY (PAE)
HALF FULL FLAG (HF)
4672 drw 03
Figure 1. Block Diagram of Single 8,192 x 18 and 16,384 x 18 Synchronous FIFO
3
IDT72V255LA/72V265LA 3.3 VOLT CMOS SuperSync FIFO™
8,192 x 18, 16,384 x 18
COMMERCIAL AND INDUSTRIAL
TEMPERATURE RANGES
PIN DESCRIPTION
Symbol
D
0
–D
17
MRS
Name
Data Inputs
Master Reset
I/O
I
I
Description
Data inputs for a 18-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 program
mable 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 offsetsfrom
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 an 18-bit 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
17
V
CC
GND
O
O
4
IDT72V255LA/72V265LA 3.3 VOLT CMOS SuperSync FIFO™
8,192 x 18, 16,384 x 18
COMMERCIAL AND INDUSTRIAL
TEMPERATURE RANGES
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 +5
–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
0
Typ.
3.3
0
Max.
3.6
0
5.0
0.8
70
85
Unit
V
V
V
V
°C
°C
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.
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°C to +70°C; Industrial: V
CC
= 3.3V
±
0.3V, T
A
= -40°C to +85°C)
IDT72V255LA
IDT72V265LA
Com’l & Ind’l
(1)
t
CLK
= 10, 15, 20 ns
Symbol
I
LI
I
LO
(3)
V
OH
V
OL
I
CC1
(4,5,6)
I
CC2
(4,7)
(2)
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
NOTES:
1. Industrial temperature range product for 15ns speed grade is available as a standard device.
2. Measurements with 0.4
≤
V
IN
≤
V
CC
.
3.
OE
≥
V
IH
, 0.4
≤
V
OUT
≤
V
CC
.
4. Tested with outputs disabled (I
OUT
= 0).
5. RCLK and WCLK toggle at 20 MHz and data inputs switch at 10 MHz.
6. Typical I
CC1
= 10 + 1.1*f
S
+ 0.02*C
L
*f
S
(in mA) with V
CC
= 3.3V, T
A
= 25°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.
CAPACITANCE
(T
A
= +25°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
ARM技术
京公网安备 11010802033920号
Copyright © 2005-2026 EEWORLD.com.cn, Inc. All rights reserved
电子工程世界
