and 
output flags. The output is low when the memory is
full and high when it is not full. The output is low when the memory is
empty and high when it is not empty.
SCAS251 - FEBRUARY 1989 - REVISED SEPTEMBER 1993
This 64-bit memory use advanced low-power Schottky technology and features high speed and fast fall-through times. It is organized as 16 words by 4 bits each.
A first-in, first-out (FIFO) memory is a storage device that allows data to be written into and read from its array at independent data rates. This FIFO is designed to process data at rates from 0 to 40 MHz in a bit-parallel format, word by word.
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 by 16 the number of words clocked out. 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 and output flags. The output is low when the memory is
full and high when it is not full. The output is low when the memory is
empty and high when it is not empty.
A low level on the reset (
)
input resets the internal stack-control pointers and also sets low and sets high. The Q outputs are not reset
to any specific logic level. The first low-to-high transition on
LDCK, after either a pulse or from
an empty condition, causes 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 at high
impedance when the output-enable (OE) input is low. OE does not
affect the or output flags. Cascading is easily
accomplished in the word-width direction but is not possible in the
word-depth direction.
The SN74ALS232B is characterized for operation from 0°C to 70°C.