3
COMMERCIAL TEMPERATURE RANGE
IDT72V3653/72V3663/72V3673 3.3V CMOS SyncFIFO
TM
WITH
BUS-MATCHING 2,048 x 36, 4,096 x 36, and 8,192 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.
Communication between each port may bypass the FIFO via two mailbox
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.
Two kinds of reset are available on these FIFOs: Reset and Partial Reset.
Reset initializes the read and write pointers to the first location of the memory array
and selects serial flag programming, parallel flag programming, or one of five
possible default flag offset settings, 8, 16, 64, 256 or 1,024.
Partial Reset also sets the read and write pointers to the first location of the
memory. Unlike Reset, any settings existing prior to Partial Reset (i.e.,
programming method and partial flag default offsets) are retained. Partial Reset
is useful since it permits flushing of the FIFO memory without changing any
configuration settings.
The FIFO has Retransmit capability, a Retransmit is performed after four
clock cycles of CLKA and CLKB, by taking the Retransmit pin, RT LOW while
the Retransmit Mode pin, RTM is HIGH. When a Retransmit is performed the
read pointer is reset to the first memory location.
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
combined Full/Input Ready Flag (FF/IR). The EF and FF functions are
selected 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 indicates when the FIFO contains more than
a selected number of words.
FF/IR and AF are two-stage synchronized to the port clock that writes data
into its array. EF/OR and AE are two-stage synchronized to the port clock that
reads data from its array. Programmable offsets for AE and AF are loaded
in parallel using Port A or in serial via the SD input. Five default offset settings
are also provided. The AE threshold can be set at 8, 16, 64, 256 or 1,024
locations from the empty boundary and the AF threshold can be set at 8, 16,
64, 256 or 1,024 locations from the full boundary. All these choices are made
using the FS0, FS1 and FS2 inputs during Reset.
Interspersed Parity is available and can be selected during a Master Reset
of the FIFO. If Interspersed Parity is selected then during parallel programming
of the flag offset values, the device will ignore data line A8. If Non-Interspersed
Parity is selected then data line A8 will become a valid bit.
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 (I
CC) is at a minimum. Initiating any operation (by activating control
inputs) will immediately take the device out of the Power Down state.
The IDT72V3653/72V3663/72V3673 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 high speed, submicron CMOS
technology.
