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.