SN74ACT7802

1024

× 18 STROBED FIRST-IN, FIRST-OUT MEMORY

SCAS187D – AUGUST 1990 – REVISED APRIL 1998

4

POST OFFICE BOX 655303

functional block diagram

OE

D0–D17

UNCK

Q0–Q17

AF/AE

HF

LDCK

EMPTY

FULL

RESET

DAF

Read

Control

Write

Control

Reset

Logic

Status-

Flag

Logic

Read

Pointer

Write

Pointer

Location 1023

Location 2

Location 1

Location 1024

1024

× 18 RAM

Terminal Functions

TERMINAL

I/O

DESCRIPTION

NAME

NO.†

I/O

DESCRIPTION

AF/AE

33

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 the almost-empty almost-full offset (X). AF/AE is high when memory contains X

or fewer words or (1024 – X) or more words. AF/AE is high after reset.

DAF

27

I

Define almost-full flag. The high-to-low transition of DAF stores the binary value of data inputs as the

AF/AE offset value (X). With DAF held low, a low pulse on RESET defines AF/AE using X.

D0–D17

7–15, 17,

19–26

I

18-bit data input port

EMPTY

66

O

Empty flag. EMPTY is low when the FIFO is empty. A FIFO reset also causes EMPTY to go low.

FULL

35

O

Full flag. FULL is low when the FIFO is full. A FIFO reset causes FULL to go high.

HF

36

O

Half-full flag. HF is high when the FIFO memory contains 512 or more words. HF is low after reset.

LDCK

29

I

Load clock. Data is written to the FIFO on the rising edge of LDCK when FULL is high.

OE

2

I

Output enable. When OE is low, the data outputs are in the high-impedance state.

Q0–Q17

38–39, 41–42,

44, 46–47,

49–50, 52–53,

55–56, 58–59,

61, 63–64

O

18-bit data-output port

RESET

1

I

Reset. A low level on RESET resets the FIFO and drives AF/AE and FULL high and HF and EMPTY low.

UNCK

5

I

Unload clock. Data is read from the FIFO on the rising edge of UNCK when EMPTY is high.

† Terminal numbers listed are for the FN package.