SCAS253 - MARCH 1990 - REVISED JUNE 1992
This 80-bit memory uses advanced low-power Schottky technology and features high speed and a fast fall-through time. It is organized as 16 words by 5 bits.
A 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. 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 contains 15 data words.
The output is low
when the memory is empty and high when it is not empty. The output is low when one word
remains in memory.
A low level on the reset (
)
input resets the internal stack control pointers and also sets low and sets , , and 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 output flags. Cascading is easily accomplished in the
word-width direction but is not possible in the word-depth direction.
The SN74ALS233B is characterized for operation from 0°C to 70°C.