TI SN74ACT7808

SN74ACT7808
2048 × 9 STROBED FIRST-IN, FIRST-OUT MEMORY
SCAS205D – FEBRUARY 1991 – REVISED APRIL 1998
D
D
D
D
D
Load Clocks and Unload Clocks Can Be
Asynchronous or Coincident
2048 Words by 9 Bits
Low-Power Advanced CMOS Technology
Fast Access Times of 15 ns With a 50-pF
Load
Programmable Almost-Full/Almost-Empty
Flag
D
D
D
D
D
D
Expansion Logic for Depth Cascading
Empty, Full, and Half-Full Flags
Fall-Through Time of 20 ns Typical
Data Rates up to 50 MHz
3-State Outputs
Package Options Include 44-Pin Plastic
Leaded Chip Carrier (FN), 64-Pin Thin Quad
Flat (PM), and Reduced-Height 64-Pin Quad
Flat (PAG) Packages
description
A FIFO memory is a storage device that allows data to be written into and read from its array at independent
data rates. The SN74ACT7808 is a 2048-word by 9-bit FIFO designed for high speed and fast access times.
It processes data at rates up to 50 MHz and access times of 15 ns in a bit-parallel format.
Data is written into memory on a low-to-high transition at the load-clock (LDCK) input and is read out on a
low-to-high transition at the unload-clock (UNCK) input. The memory is full when the number of words clocked
in exceeds the number of words clocked out by 2048. When the memory is full, LDCK signals have no effect
on the data residing in memory. When the memory is empty, UNCK signals have no effect.
Status of the FIFO memory is monitored by the full (FULL), empty (EMPTY), half-full (HF), and
almost-full/almost-empty (AF/AE) flags. The FULL output is low when the memory is full and high when the
memory is not full. The EMPTY output is low when the memory is empty and high when it is not empty. The HF
output is high when the FIFO contains 1024 or more words and is low when it contains 1023 or fewer words.
The AF/AE status flag is a programmable flag. The first one or two low-to-high transitions of LDCK after reset
can be used to program the almost-empty offset value (X) and the almost-full offset value (Y) if program enable
(PEN) is low. The AF/AE flag is high when the FIFO contains X or fewer words or (2048 – Y) or more words.
The AF/AE flag is low when the FIFO contains between (X + 1) and (2047 – Y) words.
A low level on the reset (RESET) input resets the internal stack pointers and sets FULL high, AF/AE high, HF
low, and EMPTY low. The Q outputs are not reset to any specific logic level.
The first word loaded into empty memory causes EMPTY to go high and the data to appear on the Q outputs.
It is important to note that the first word does not have to be unloaded. Data outputs are noninverting with respect
to the data inputs and are in the high-impedance state when the output-enable (OE) input is low. OE does not
affect the output flags.
Cascading is easily accomplished in the word-width and word-depth directions. When not using the FIFO in
depth expansion, cascade enable (CASEN) must be tied high.
The FIFO must be reset upon power up.
The SN74ACT7808 is characterized for operation from 0°C to 70°C.
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
Copyright  1998, Texas Instruments Incorporated
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of Texas Instruments
standard warranty. Production processing does not necessarily include
testing of all parameters.
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
1
SN74ACT7808
2048 × 9 STROBED FIRST-IN, FIRST-OUT MEMORY
SCAS205D – FEBRUARY 1991 – REVISED APRIL 1998
VCC
HF
AF/AE
GND
PEN
RESET
VCC
XO
OE
GND
Q0
FN PACKAGE
(TOP VIEW)
6
7
5 4
3 2
1 44 43 42 41 40
39
8
38
9
37
10
36
11
35
12
34
13
33
14
32
15
31
16
30
Q1
VCC
Q2
Q3
GND
Q4
VCC
Q5
Q6
GND
Q7
Q8
29
17
18 19 20 21 22 23 24 25 26 27 28
GND
LDCK
DP9
XI
FULL
EMPTY
FL
CASEN
UNCK
D0
D1
D2
GND
D3
D4
D5
VCC
D6
D7
D8
Q2
Q3
GND
GND
Q4
VCC
VCC
Q5
Q6
GND
GND
Q7
NC
Q1
VCC
VCC
PAG OR PM PACKAGE
(TOP VIEW)
64 63 62 61 60 59 58 57 56 55 54 53 52 51 50 49
NC
Q0
GND
GND
OE
XO
VCC
VCC
RESET
PEN
GND
GND
AF/AE
HF
VCC
VCC
1
48
2
47
3
46
4
45
5
44
6
43
7
42
8
41
9
40
10
39
11
38
12
37
13
36
14
35
15
34
16
33
D6
D7
D8
NC
NC
D0
D1
D2
GND
GND
D3
D4
NC
D5
VCC
VCC
17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32
NC – No internal connection
2
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• DALLAS, TEXAS 75265
NC
Q8
VCC
VCC
UNCK
CASEN
NC
FL
EMPTY
FULL
XI
DP9
LDCK
GND
GND
NC
SN74ACT7808
2048 × 9 STROBED FIRST-IN, FIRST-OUT MEMORY
SCAS205D – FEBRUARY 1991 – REVISED APRIL 1998
logic symbol†
1
RESET
LDCK
UNCK
OE
PEN
FL
CASEN
XI
DP9
D0
D1
D2
D3
D4
D5
D6
D7
D8
Φ
FIFO 2048 × 9
SN74ACT7808
RESET
19
26
42
2
24
25
21
20
7
FULL
LDCK
HALF FULL
UNCK
ALMOST FULL/EMPTY
EMPTY
EN1
22
5
4
23
AF/AE
EMPTY
PROGRAM ENABLE
FIRST LOAD
EXPANSION OUT
43
XO
CASCADE ENABLE
EXPANSION IN
DATA PIN 9
0
0
40
8
39
9
37
11
36
12
Data
Data
34
1
13
32
15
31
16
29
17
FULL
HF
8
8
28
Q0
Q1
Q2
Q3
Q4
Q5
Q6
Q7
Q8
† This symbol is in accordance with ANSI/IEEE Std 91-1984 and IEC Publication 617-12.
Pin numbers shown are for the FN package.
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• DALLAS, TEXAS 75265
3
SN74ACT7808
2048 × 9 STROBED FIRST-IN, FIRST-OUT MEMORY
SCAS205D – FEBRUARY 1991 – REVISED APRIL 1998
functional block diagram
OE
D0–D8
UNCK
Location 1
Location 2
Read
Pointer
2048 × 9 RAM
LDCK
Write
Pointer
Location 2047
Location 2048
DP9
Q0–Q8
RESET
PEN
FL
Reset
Logic
EMPTY
Expansion
and
Status-Flag
Logic
CASEN
HF
AF/AE
XO
XI
4
FULL
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SN74ACT7808
2048 × 9 STROBED FIRST-IN, FIRST-OUT MEMORY
SCAS205D – FEBRUARY 1991 – REVISED APRIL 1998
Terminal Functions
TERMINAL
NAME
I/O
DESCRIPTION
AF/AE
O
Almost-full/almost-empty flag. Depth-offset values can be programmed for AF/AE or the default value of 256 can be
used for both the almost-empty offset (X) and the almost-full offset (Y). AF/AE is high when memory contains X or fewer
words or (2048 – Y) or more words. AF/AE is high after reset.
CASEN†
I
Cascade enable. When multiple SN74ACT7808 devices are depth cascaded, every device must have CASEN tied low.
CASEN must be tied high when a device is not used in depth expansion.
D0–D8
I
Nine-bit data input port
DP9
I
DP9 is used as the most significant bit when programming the AF/AE offset values.
EMPTY
O
Empty flag. EMPTY is low when the FIFO memory is empty. A FIFO reset also causes EMPTY to go low.
FL†
I
First load. When multiple SN74ACT7808 devices are depth cascaded, the first device in the chain must have its FL
input tied low and all other devices must have their FL inputs tied high.
FULL
O
Full flag. FULL is low when the FIFO is full. A FIFO reset causes FULL to go high.
HF
O
Half-full flag. HF is high when the FIFO memory contains 1024 or more words. HF is low after reset.
LDCK
I
Load clock. Data is written to the FIFO on the rising edge of LDCK when FULL is high.
OE
I
Output enable. When OE is low, D0–D8 are in the high-impedance state.
PEN
I
Program enable. After reset and before the first word is written to the FIFO, the binary value on D0–D8 and DP9 is
latched as an AF/AE offset value when PEN is low and LDCK is high.
Q0–Q8
O
Nine-bit data output port
RESET
I
Reset. A low level on RESET resets the FIFO and drives FULL and AF/AE high and HF and EMPTY low.
UNCK
I
Unload clock. Data is read from the FIFO on the rising edge of UNCK when EMPTY is high.
XI†
I
XO†
O
Expansion input (XI) and expansion output (XO). When multiple SN74ACT7808 devices are depth cascaded, the XO
of one device must be connected to the XI of the next device in the chain
chain. The XO of the last device in the chain is
connected to the XI of the first device in the chain.
† See Figures 6 and 7 for application information on FIFO word-width and word-depth expansions, respectively.
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5
SN74ACT7808
2048 × 9 STROBED FIRST-IN, FIRST-OUT MEMORY
SCAS205D – FEBRUARY 1991 – REVISED APRIL 1998
offset values for AF/AE
The AF/AE flag has two programmable limits: the almost-empty offset value (X) and the almost-full offset
value (Y). They can be programmed after the FIFO is reset and before the first word is written to memory. If the
offsets are not programmed, the default values of X = Y = 256 are used. The AF/AE flag is high when the FIFO
contains X or fewer words or (2048 – Y) or more words.
To program the offset values, program enable (PEN) can be brought low after reset only when LDCK is low. On
the following low-to-high transition of LDCK, the binary value on D0–D8 and DP9 is stored as the almost-empty
offset value (X) and the almost-full offset value (Y). Holding PEN low for another low-to-high transition of LDCK
reprograms Y to the binary value on D0–D8 and DP9 at the time of the second LDCK low-to-high transition.
Writes to the FIFO memory are disabled while the offsets are programmed. A maximum value of 1023 can be
programmed for either X or Y (see Figure 1). To use the default values of X = Y = 256, PEN must be held high.
RESET
LDCK
ÎÎ
ÎÎÎÎÎÎÎÎ
ÉÉÉÉ
ÎÎ
ÎÎÎÎÎÎÎÎ
ÎÎ
ÎÎÎÎÎÎÎÎ
PEN
D0–D8
DP9
EMPTY
Don’t Care
ÌÌÌÌÌÌÌÌ
ÌÌ
ÌÌÌÌÌÌÌÌ
ÌÌ
ÌÌÌÌÌÌÌÌ
ÌÌ
ÌÌÌÌÌÌÌÌ
ÌÌ
ÌÌÌÌÌÌÌÌ
ÌÌ
ÏÏÏÏÏ
ÏÏÏÏÏ
ÏÏÏÏÏ
Don’t Care
Don’t Care
X and Y
Y
X and Y MSB
Y MSB
Figure 1. Programming X and Y Separately
6
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• DALLAS, TEXAS 75265
RESET
PEN
1
0
CASEN
1
0
POST OFFICE BOX 655303
ÌÌ
ÌÌ
ÌÌÌÌ
ÌÌÌÌ
ÌÌÌÌ
ÌÌ
ÌÌ
ÌÌÌÌ
ÌÌÌÌ
ÌÌ
ÌÌ
ÌÌ
ÌÌ
ÌÌ
ÌÌ
ÌÌ
ÌÌ
ÌÌ
ÌÌ
ÌÌ
ÌÌ
ÌÌ
ÌÌ
ÌÌ
ÌÌ
ÌÌ
ÌÌ
LDCK
D0–D8
W1
W2
W
(X+1)
W1024
W
(2048–Y)
Don’t Care
W2048
UNCK
W1
W2
W
(Y+1)
W
(Y+2)
W1025
W1026
W
(2048–X)
W
(2049–x)
ÌÌ
ÌÌ
ÌÌ
ÌÌ
ÌÌ
ÌÌÌÌÌÌÌÌÌÌÌÌ
ÌÌÌÌÌÌÌÌÌÌ
ÌÌ
• DALLAS, TEXAS 75265
Q0–Q8
W2047
W2048
EMPTY
HF
FULL
Figure 2
Define the AF/AE Flag Using
the Default Value or X and Y
Figure 2. Read
7
SCAS205D – FEBRUARY 1991 – REVISED APRIL 1998
AF/AE
SN74ACT7808
2048 × 9 STROBED FIRST-IN, FIRST-OUT MEMORY
OE
SN74ACT7808
2048 × 9 STROBED FIRST-IN, FIRST-OUT MEMORY
SCAS205D – FEBRUARY 1991 – REVISED APRIL 1998
absolute maximum ratings over operating free-air temperature range (unless otherwise noted)†
Supply voltage range, VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –0.5 V to 7 V
Input voltage range, VI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –0.5 V to 7 V
Voltage range applied to a disabled 3-state output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –0.5 V to 5.5 V
Package thermal impedance, θJA (see Note 1): FN package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46°C/W
PAG package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58°C/W
PM package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67°C/W
Storage temperature range, Tstg . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –65°C to 150°C
† Stresses beyond those listed under “absolute maximum ratings” may cause permanent damage to the device. These are stress ratings only, and
functional operation of the device at these or any other conditions beyond those indicated under “recommended operating conditions” is not
implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
NOTE 1: The package thermal impedance is calculated in accordance with JESD 51.
recommended operating conditions
’ACT7808-20
’ACT7808-25
’ACT7808-30
’ACT7808-40
MIN
MAX
MIN
MAX
MIN
MAX
MIN
MAX
4.5
5.5
4.5
5.5
4.5
5.5
4.5
5.5
UNIT
VCC
Supply voltage
VIH
High level input voltage
High-level
VIL
IOH
Low-level input voltage
0.8
0.8
0.8
0.8
V
High-level output current
–8
–8
–8
–8
mA
IOL
Low level output current
Low-level
16
16
16
16
8
8
8
8
TA
Operating free-air temperature
XI
3.85
3.85
3.85
3.85
2
2
2
2
Other inputs
Q outputs
Flags
0
70
0
70
0
70
0
V
V
70
mA
°C
electrical characteristics over recommended operating free-air temperature range (unless
otherwise noted)
PARAMETER
VOH
VOL
II
IOZ
ICC
∆ICC§
Ci
Flags
Q outputs
TEST CONDITIONS
VCC = 4.5 V,
VCC = 4.5 V,
IOH = –8 mA
IOL = 8 mA
VCC = 4.5 V,
VCC = 5.5 V,
IOL = 16 mA
VI =VCC or 0
VCC = 5.5 V,
VCC = 5.5 V,
VO =VCC or 0
VI = VCC – 0.2 V or 0
VCC = 5.5 V,
VI = 0,
One input at 3.4 V,
MIN
TYP‡
MAX
2.4
V
0.5
0.5
Other inputs at VCC or GND
f = 1 MHz
4
Co
UNIT
V
±5
µA
±5
µA
400
µA
1
mA
pF
VO = 0,
f = 1 MHz
8
pF
‡ All typical values are at VCC = 5 V, TA = 25°C.
§ This is the increase in supply current for each input, excluding XI, that is at one of the specified TTL voltage levels rather 0 V or VCC.
8
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
SN74ACT7808
2048 × 9 STROBED FIRST-IN, FIRST-OUT MEMORY
SCAS205D – FEBRUARY 1991 – REVISED APRIL 1998
timing requirements over recommended operating conditions (unless otherwise noted) (see
Figures 1 through 3)
’ACT7808-20
MIN
fclock
tw
Clock frequency
Pulse duration
Setup time
th
Hold time
’ACT7808-25
MIN
MAX
50
’ACT7808-30
MIN
40
MAX
’ACT7808-40
MIN
33.3
MAX
25
LDCK high or low
8
9
11
13
UNCK high or low
8
9
11
13
PEN low
9
9
11
13
RESET low
tsu
MAX
10
13
16
19
D0–D8, DP9 before LDCK↑
5
5
5
5
LDCK inactive
before RESET high
5
5
5
5
PEN before LDCK↑
5
5
5
5
D0–D8, DP9 after LDCK↑
0
0
0
0
LDCK inactive
after RESET high
5
5
5
5
PEN low after LDCK↑
4
4
4
4
PEN high after LDCK low
0
0
0
0
UNIT
MHz
ns
ns
ns
switching characteristics over recommended ranges of supply voltage and operating free-air
temperature, CL = 50 pF (unless otherwise noted) (see Figure 3)
PARAMETER
FROM
(INPUT)
fmax
LDCK or UNCK
TO
(OUTPUT)
’ACT7808-20
TYP†
MAX
MIN
50
40
LDCK↑
tpd
UNCK↑
5
Any Q
UNCK↑
Any Q
tPLH
LDCK↑
EMPTY
tPHL
RESET low
tPLH
tpd
d
tPLH
tPHL
tPLH
tPHL
ten
tdis
ten
tdis
EMPTY
FULL
UNCK↑
RESET low
LDCK↑
UNCK↑
’ACT7808-30
MIN
MAX
33.3
’ACT7808-40
MIN
MAX
25
5
22
5
25
5
28
15
4.5
18
4.5
20
4.5
22
4
15
4
17
4
19
4
21
2
15
2
17
2
19
2
21
2
16
2
18
2
20
2
22
4
15
4
17
4
19
4
21
4
14
4
16
4
18
4
20
2
18
2
20
2
22
2
24
2
16
2
18
2
20
2
22
2
16
2
18
2
20
2
22
11
FULL
AF/AE
UNIT
MHz
10
UNCK↑
LDCK↑
MAX
20
4.5
tpd‡
’ACT7808-25
MIN
ns
ns
ns
ns
ns
ns
RESET low
AF/AE
0
10
0
12
0
14
0
16
LDCK↑
HF
2
19
2
21
2
23
2
25
2
16
2
18
2
20
2
22
2
12
2
14
2
16
2
18
XO
2
11
2
13
2
15
2
17
ns
LDCK↑
XO
2
11
2
13
2
15
2
17
ns
OE
Any Q
1
10
1
12
1
14
1
16
ns
OE
Any Q
1
9
1
11
1
13
1
15
ns
XI high
Any Q
3
13
3
15
3
17
3
19
ns
XO high
Any Q
4
ns
UNCK↑
RESET low
UNCK↑
HF
4
4
4
ns
ns
† All typical values are at VCC = 5 V, TA = 25°C.
‡ This parameter is measured with CL = 30 pF (see Figure 4).
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9
SN74ACT7808
2048 × 9 STROBED FIRST-IN, FIRST-OUT MEMORY
SCAS205D – FEBRUARY 1991 – REVISED APRIL 1998
operating characteristics, VCC = 5 V, TA = 25°C
PARAMETER
Cpd
TEST CONDITIONS
Power dissipation capacitance per FIFO channel
Outputs enabled
CL = 50 pF,
TYP
f = 5 MHz
UNIT
91
pF
PARAMETER MEASUREMENT INFORMATION
7V
PARAMETER
S1
ten
500 Ω
From Output
Under Test
Test
Point
CL = 50 pF
(see Note A)
tdis
tpd
500 Ω
S1
tPZH
tPZL
tPHZ
tPLZ
tPLH
tPHL
Open
Closed
Open
Closed
Open
Open
tw
LOAD CIRCUIT
3V
Input
0V
1.5 V
VOLTAGE WAVEFORMS
PULSE DURATION
0V
tsu
th
3V
Data
Input
1.5 V
1.5 V
0V
3V
Output
Control
tPZL
3V
1.5 V
1.5 V
1.5 V
0V
tPLH
1.5 V
1.5 V
tPZH
1.5 V
VOL
Output
Waveform 2
S1 at Open
VOL + 0.3 V
1.5 V
VOH
VOH – 0.3 V
≈0V
NOTE A: CL includes probe and jig capacitance.
Figure 3. Load Circuit and Voltage Waveforms
• DALLAS, TEXAS 75265
VOL
tPHZ
VOLTAGE WAVEFORMS
ENABLE AND DISABLE TIMES
VOLTAGE WAVEFORMS
PROPAGATION DELAY TIMES
POST OFFICE BOX 655303
tPLZ
≈ 3.5 V
Output
Waveform 1
S1 at 7 V
tPHL
VOH
10
1.5 V
0V
VOLTAGE WAVEFORMS
SETUP AND HOLD TIMES
Output
1.5 V
3V
Timing
Input
Input
1.5 V
SN74ACT7808
2048 × 9 STROBED FIRST-IN, FIRST-OUT MEMORY
SCAS205D – FEBRUARY 1991 – REVISED APRIL 1998
TYPICAL CHARACTERISTICS
PROPAGATION DELAY TIME
vs
LOAD CAPACITANCE
SUPPLY CURRENT
vs
CLOCK FREQUENCY
160
VCC = 5 V
RL = 500 Ω
TA = 25°C
typ + 6
TA = 75°C
CL = 0 pF
140
I CC(f) – Supply Current – mA
t pd – Propagation Delay Time – ns
typ + 8
typ + 4
typ + 2
typ
VCC = 5.5 V
VCC = 5 V
120
100
80
VCC = 4.5 V
60
40
20
typ – 2
0
50
100
150
200
250
300
0
0
10
CL – Load Capacitance – pF
20
30
40
50
60
70
80
fclock – Clock Frequency – MHz
Figure 4
Figure 5
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• DALLAS, TEXAS 75265
11
SN74ACT7808
2048 × 9 STROBED FIRST-IN, FIRST-OUT MEMORY
SCAS205D – FEBRUARY 1991 – REVISED APRIL 1998
APPLICATION INFORMATION
LDCK
FULL
SN74ACT7808
LDCK
UNCK
EMPTY
FULL
OE
D9–D17
D0–D8
CASEN
Q0–Q8
UNCK
EMPTY
OE
Q9–Q17
H
SN74ACT7808
LDCK
UNCK
EMPTY
FULL
OE
D0–D8
D0–D8
CASEN
Q0–Q8
H
Figure 6. Word-Width Expansion: 2048 × 18 Bits
12
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
Q0–Q8
SN74ACT7808
2048 × 9 STROBED FIRST-IN, FIRST-OUT MEMORY
SCAS205D – FEBRUARY 1991 – REVISED APRIL 1998
APPLICATION INFORMATION
depth cascading (see Figure 7)
The SN74ACT7808 provides expansion logic necessary for cascading an unlimited number of the FIFOs in
depth. CASEN must be low on all FIFOs used in depth expansion. FL must be tied low on the first FIFO in the
chain; all others must have FL tied high. The expansion-out (XO) output of a FIFO must be tied to the
expansion-in (XI) input of the next FIFO in the chain. The XO output of the last FIFO is tied to the XI input of
the first FIFO to complete the loop. Data buses are common to each FIFO in the chain. A composite EMPTY
and FULL signal must be generated to indicate boundary conditions.
RESET
OE
L
FL
L
H
CASEN
FL
H
CASEN
FL
L
CASEN
SN74ACT7808
SN74ACT7808
SN74ACT7808
XI
XO
XI
XO
XI
XO
RESET
OE
RESET
OE
RESET
OE
D0–D8 Q0–Q8
LDCK
UNCK
9
FULL EMPTY
D0–D8
L
D0–D8 Q0–Q8
9
LDCK
UNCK
D0–D8 Q0–Q8
9
9
LDCK
UNCK
FULL EMPTY
FULL EMPTY
9
9
9
9
Q0–Q8
UNCK
LDCK
FULL
EMPTY
Figure 7. Depth Cascading to Form a 6K × 9 FIFO
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
13
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