SN74ACT7802

1024

× 18 STROBED FIRST-IN, FIRST-OUT MEMORY

SCAS187D – AUGUST 1990 – REVISED APRIL 1998

2

POST OFFICE BOX 655303

22 23

NC

Q3

Q2

GND

Q1

Q0

HF

FULL

GND

GND

AF/AE

NC

NC

LDCK

GND

NC

60

59

58

57

56

55

54

53

52

51

50

49

48

47

46

45

44

43

42

41

24

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

NC

GND

GND

Q16

Q17

EMPTY

GND

RESET

OE

NC

NC

UNCK

GND

D17

D16

D15

NC

NC

25 26 27 28

PN PACKAGE

(TOP VIEW)

79 78 77 76 75

80

74

72 71 70

73

29 30 31 32 33

69 68

21

67 66 65 64

34 35 36 37 38 39 40

63 62 61

NC – No internal connection

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 SN74ACT7802 is a 1024-word by 18-bit FIFO for high-speed applications. It processes data

in a bit-parallel format at rates up to 40 MHz and access times of 30 ns.

Data is written into the FIFO memory on a low-to-high transition on the load-clock (LDCK) input and is read out

on a low-to-high transition on the unload-clock (UNCK) input. The memory is full when the number of words

clocked in exceeds by 1024 the number of words clocked out. When the memory is full, LDCK has no effect on

the data in the memory; when the memory is empty, UNCK has no effect.

A low level on the reset (RESET) input resets the FIFO internal clock stack pointers and sets full (FULL) high,

almost full/almost empty (AF/AE) high, half full (HF) low, and empty (EMPTY) low. The Q outputs are not reset

to any specific logic level. The FIFO must be reset upon power up. The Q outputs are noninverting and are in

the high-impedance state when the output-enable (OE) input is low.

When writing to the FIFO after a reset pulse or when the FIFO is empty, the first active transition on LDCK drives

EMPTY high and causes the first word written to the FIFO to appear on the Q outputs. An active transition on

UNCK is not required to read the first word written to the FIFO. Each subsequent read from the FIFO requires

an active transition on UNCK.

The SN74ACT7802 can be cascaded in the word-width direction but not in the word-depth direction.

The SN74ACT7802 is characterized for operation from 0

°C to 70°C.