Member of the Texas Instruments

WidebusE Family

Low-Power Advanced CMOS Technology

Operates From 3-V to 3.6-V VCC

Load Clock and Unload Clock Can Be

Asynchronous or Coincident

Full, Empty, and Half-Full Flags

Programmable Almost-Full/Almost-Empty

Flag

Fast Access Times of 18 ns With a 50-pF

Load and All Data Outputs Switching

Simultaneously

Data Rates up to 40 MHz

3-State Outputs

Pin-to-Pin Compatible With SN74ACT7804,

SN74ACT7806, and SN74ACT7814

Packaged in Shrink Small-Outline 300-mil

Package Using 25-mil Center-to-Center

Spacing

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 SN74ALVC7806 is

an 18-bit FIFO with high speed and fast access

times. Data is processed at rates up to 40 MHz

with access times of 18 ns in a bit-parallel format.

These memories are designed for 3-V to 3.6-V

VCC operation.

Data is written into memory on a low-to-high

transition of the load clock (LDCK) and is read out

on a low-to-high transition of the unload clock

(UNCK). The memory is full when the number of words clocked in exceeds the number of words clocked out

by 256. When the memory is full, LDCK has no effect on the data residing in memory. When the memory is

empty, UNCK has no effect.

Status of the FIFO memory is monitored by the full (FULL), empty (EMPTY), half-full (HF), and almostfull/

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 whenever the FIFO contains 128 or more words and low when it contains 127 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 are 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 (256 – Y) or more words. The AF/AE flag

is low when the FIFO contains between (X + 1) and (255 – Y) words.