4
COMMERCIAL AND INDUSTRIAL
TEMPERATURE RANGES
IDT72V275/72V285 3.3V CMOS SUPERSYNC FIFO
TM
32,768 x 18 and 65,536 x 18
PIN DESCRIPTION
Symbol Name I/O Description
D0–D17 Data Inputs I Data inputs for a 18-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 register to
all zeroes. During Partial Reset, the existing mode (IDT or FWFT), programming
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
Input Ready not the FIFO memory 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
Output Ready not the FIFO memory 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
Almost-Full Flag total word capacity of the FIFO 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,
Almost-Empty Flag which is stored in the 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–Q17 Data Outputs O Data outputs for an 18-bit bus.
VCC Power +3.3 Volt power supply pins.
GND Ground Ground pins.
