3
COMMERCIAL TEMPERATURERANGE
IDT72V3623/72V3633/72V3643 CMOS 3.3V SyncBiFIFOTM WITH BUS-MATCHING
256 x 36, 512 x 36, 1,024 x 36
each port are independent of one another and can be asynchronous or
coincident. The enables for each port are arranged to provide a simple
bidirectional interface between microprocessors and/or buses with synchro-
nous control.
CommunicationbetweeneachportmaybypasstheFIFOviatwomailbox
registers. The mailbox registers' width matches the selected Port B bus width.
Each mailbox register has a flag (
MBF1 and MBF2) to signal when new mail
has been stored.
TwokindsofresetareavailableontheseFIFOs: ResetandPartialReset.
Resetinitializesthereadandwritepointerstothefirstlocationofthememoryarray
and selects serial flag programming, parallel flag programming, or one of three
possible default flag offset settings, 8, 16 or 64.
PartialResetalsosetsthereadandwritepointerstothefirstlocationofthe
memory. Unlike Reset, any settings existing prior to Partial Reset (i.e.,
programmingmethodandpartialflagdefaultoffsets)areretained. PartialReset
is useful since it permits flushing of the FIFO memory without changing any
configurationsettings.
These devices have two modes of operation: In the IDT Standard mode,
the first word written to an empty FIFO is deposited into the memory array. A
read operation is required to access that word (along with all other words
residing in memory). In the First Word Fall Through mode (FWFT), the first
word written to an empty FIFO appears automatically on the outputs, no read
operation required (Nevertheless, accessing subsequent words does neces-
sitate a formal read request). The state of the BE/
FWFT pin during Reset
determines the mode in use.
The FIFO has a combined Empty/Output Ready Flag (
EF/OR ) and a
combinedFull/InputReadyFlag(
FF/IR). TheEFandFFfunctionsareselected
in the IDT Standard mode.
EF indicates whether or not the FIFO memory is
empty.
FF shows whether the memory is full or not. The IR and OR functions
are selected in the First Word Fall Through mode. IR indicates whether or not
the FIFO has available memory locations. OR shows whether the FIFO has
data available for reading or not. It marks the presence of valid data on the
outputs.
The FIFO has a programmable Almost-Empty flag (
AE) and a program-
mable Almost-Full flag (
AF). AE indicates when a selected number of words
remain in the FIFO memory.
AF indicateswhentheFIFOcontainsmorethan
a selected number of words.
FF/IRandAFaretwo-stagesynchronizedtotheportclockthatwritesdata
into its array.
EF/ORandAEaretwo-stagesynchronizedtotheportclockthat
reads data from its array. Programmable offsets for
AE and AF are loaded in
parallelusingPortAorinserialviatheSDinput.TheSerialProgrammingMode
pin(
SPM)makesthisselection.Threedefaultoffsetsettingsarealsoprovided.
The
AEthreshold can be set at 8, 16 or 64 locations from the empty boundary
and the
AFthresholdcanbesetat8,16or64locationsfromthefullboundary.
All these choices are made using the FS0 and FS1 inputs during Reset.
Two or more devices may be used in parallel to create wider data paths.
In First Word Fall Through mode, more than one device may be connected in
series to create greater word depths. The addition of external components is
unnecessary.
If, at any time, the FIFO is not actively performing a function, the chip will
automatically power down. During the power down state, supply current
consumption(ICC)isataminimum.Initiatinganyoperation(byactivatingcontrol
inputs) will immediately take the device out of the Power Down state.
The IDT72V3623/72V3633/72V3643 are characterized for operation from
0
°C to 70°C. Industrial temperature range (-40°C to +85°C) is available by
special order. They are fabricated using IDT’s high speed, submicron CMOS
technology.