4
COMMERCIAL AND INDUSTRIAL
TEMPERATURE RANGES
IDT72261LA/72271LA SuperSync FIFO™
16,384 x 9 and 32,768 x 9
Symbol Name I/O Description
D0–D8 Data Inputs I Data inputs for a 9-bit bus.
MRS Master Reset I MRS initializes the read and write pointers to zero and sets the output register to all zeroes.
During Master Reset, the FIFO is configured for either FWFT or IDT Standard mode, one of
two programmable flag default settings, and serial or parallel programming of the offset settings.
PRS Partial Reset I PRS initializes the read and write pointers to zero and sets the output method (serial or parallel),
and programmable flag settings are all retained.
RT Retransmit I RT asserted on the rising edge of RCLK initializes the READ pointer to zero, sets
the EF flag to
LOW (OR to HIGH in FWFT mode) temporarily and does not disturb the write pointer, programming
method, existing timing mode or programmable flag settings. RT is useful to reread data from the
first physical location of the FIFO.
FWFT/SI First Word Fall I During Master Reset, selects First Word Fall Through or IDT Standard mode. Through/Serial
In After Master Reset, this pin functions as a serial input for loading offset registers
WCLK Write Clock I When enabled by WEN, the rising edge of WCLK writes data into the FIFO and offsets into
the programmable registers for parallel programming, and when enabled by SEN, the rising
edge of WCLK writes one bit of data into the programmable register for serial programming.
WEN Write Enable I WEN enables WCLK for writing data into the FIFO memory and offset registers.
RCLK Read Clock I When enabled by REN, the rising edge of RCLK reads data from the FIFO memory and offsets
from the programmable registers.
REN Read Enable I REN enables RCLK for reading data from the FIFO memory and offset registers.
OE Output Enable I OE controls the output impedance of Qn.
SEN Serial Enable I SEN enables serial loading of programmable flag offsets.
LD Load I During Master Reset, LD selects one of two partial flag default offsets (127 or
1,023) and determines
the flag offset programming method, serial or parallel. After
Master Reset, this pin enables writing to
and reading from the offset registers.
DC Don't Care I This pin must be tied to either VCC or GND and must not toggle after Master Reset.
FF/IR Full Flag/ O In the IDT Standard mode, the FF function is selected. FF indicates whether or not the FIFO memory
Input Ready is full. In the FWFT mode, the IR function is selected. IR indicates whether or not there is space
available for writing to the FIFO memory.
EF/OR Empty Flag/ O In the IDT Standard mode, the EF function is selected. EF indicates whether or not the FIFO memory
Output Ready is empty. In FWFT mode, the OR function is selected. OR indicates whether or not there is valid data
available at the outputs.
PAF Programmable O PAF goes LOW if the number of words in the FIFO memory is more than word capacity of the FIFO
Almost-Full Flag minus the full offset value m, which is stored in the Full Offset register. There are two possible default
values for m: 127 or 1,023.
PAE Programmable O PAE goes LOW if the number of words in the FIFO memory is less than offset n, which is stored in the
Almost-Empty Flag Empty Offset register. There are two possible default values for n: 127 or 1,023. Other values for n
can be programmed into the device.
HF Half-Full Flag O HF indicates whether the FIFO memory is more or less than half-full.
Q0–Q8 Data Outputs O Data outputs for a 9-bus
VCC Power +5 Volt power supply pins.
GND Ground Ground pins.
PIN DESCRIPTION
