, 
, almost-full/almost-empty (AF/AE), and half-full (HF)
output flags. The output is low
when the memory is full and high when the memory is not full. The
output is low
when the memory is empty, and high when it is not
SCAS249 - FEBRUARY 1988 - REVISED MARCH 1990
IMPACT-X is a trademark of Texas Instruments Incorporated.
This 576-bit memory uses advanced low-power Schottky IMPACT-X TM technology and features high speed and fast fall-through times. It is organized as 64 words by 9 bits.
A FIFO memory is a storage device that allows data to be written into and read from its array at independent data rates. The function is used as a buffer to couple two buses operating at different clock 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 of the load clock (LDCK) input and is read out on a low-to-high transition of the unload clock (UNCK) input. The memory is full when the number of words clocked in exceeds by 64 the number of words clocked out. When the memory is full, LDCK signals have no effect on the data residing in memory. When the the memory is empty, UNCK signals have no effect.
Status of the FIFO memory is monitored by the , , almost-full/almost-empty (AF/AE), and half-full (HF)
output flags. The output is low
when the memory is full and high when the memory is not full. The
output is low
when the memory is empty, and high when it is not
empty. The AF/AE flag is high when the FIFO contains eight or less words or 56 or more words. The AF/AE flag is low when the FIFO contains between nine and 55 words. The HF flag is high when the FIFO contains 32 or more words and is low when the FIFO contains 31 words or less.
A low level on the reset (
)
input resets the internal stack control pointers and also sets low and high. The outputs are not reset to
any specific logic levels. The first low-to-high transition on LDCK,
either after a pulse or from
an empty condition, causes to go
high and the data to appear on the Q outputs. The first word does not
have to be unloaded. Data outputs are noninverting with respect to
the data inputs and are at a high-impedance state when the
output-enable (OE) input is low. The OE input does not effect either
the or output flags. Cascading is easily
accomplished in the word-width direction, but is not possible in the
word-depth direction.
The SN74ALS2233A is characterized for operation from 0°C to 70°C.