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Details, datasheet, quote on part number:SN74ACT7808-20
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Datasheet text preview:
SN74ACT7808 2048 × 9 STROBED FIRST-IN, FIRST-OUT MEMORY
SCAS205E FEBRUARY 1991 REVISED NOVEMBER 2001
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.
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.
Copyright 2001, Texas Instruments Incorporated
POST OFFICE BOX 655303
· DALLAS, TEXAS 75265
1
SN74ACT7808 2048 × 9 STROBED FIRST-IN, FIRST-OUT MEMORY
SCAS205E FEBRUARY 1991 REVISED NOVEMBER 2001
FN PACKAGE (TOP VIEW)
D0 D1 D2 GND D3 D4 D5 VCC D6 D7 D8
VCC HF AF/AE GND PEN RESET VCC XO OE GND Q0
6 7 8 9 10 11 12 13 14 15 16 54 32 1 44 43 42 41 40 39 38 37 36 35 34 33 32 31 30 17 29 18 19 20 21 22 23 24 25 26 27 28
Q1 VCC Q2 Q3 GND Q4 VCC Q5 Q6 GND Q7
GND LDCK DP9 XI FULL EMPTY FL CASEN UNCK 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
Q1 VCC VCC
Q2 Q3 GND GND Q4 VCC VCC Q5 Q6 GND GND Q7 NC
Q8
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
NC Q8 VCC VCC UNCK CASEN NC FL EMPTY FULL XI DP9 LDCK GND GND NC
NC D0 D1 D2 GND GND D3 D4 NC D5 VCC VCC
NC No internal connection 2
POST OFFICE BOX 655303
· DALLAS, TEXAS 75265
D6 D7 D8 NC
SN74ACT7808 2048 × 9 STROBED FIRST-IN, FIRST-OUT MEMORY
SCAS205E FEBRUARY 1991 REVISED NOVEMBER 2001
logic symbol
FIFO 2048 × 9 SN74ACT7808 RESET LDCK UNCK EN1 PROGRAM ENABLE FIRST LOAD EXPANSION OUT 43 XO FULL HALF FULL ALMOST FULL/EMPTY EMPTY 22 5 4 23 FULL HF AF/AE EMPTY
1 RESET LDCK UNCK OE PEN FL CASEN XI DP9 19 26 42 2 24 25 21 20
CASCADE ENABLE EXPANSION IN DATA PIN 9
D0 D1 D2 D3 D4 D5 D6 D7 D8
7 8 9 11 12 13 15 16 17
0
0
40 39 37 36
Q0 Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8
Data
Data
1
34 32 31 29
8
8
28
This symbol is in accordance with ANSI/IEEE Std 91-1984 and IEC Publication 617-12. Pin numbers shown are for the FN package.
POST OFFICE BOX 655303
· DALLAS, TEXAS 75265
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