19
IDT72V263/273/283/293/103/113 3.3V HIGH DENSITY SUPERSYNC IITM NARROW BUS FIFO
8K x 18, 16K x 9/18, 32K x 9/18, 64K x 9/18, 128K x 9/18, 256K x 9/18, 512K x9
COMMERCIAL AND INDUSTRIAL
TEMPERATURE RANGES
IDT72V223/233/243/253/263/273/283/293 3.3V HIGH DENSITY SUPERSYNC IITM NARROW BUS FIFO
512 x 18, 1K x 9/18, 2K x 9/18, 4K x 9/18, 8K x 9/18, 16K x 9/18, 32K x 9/18, 64K x 9/18, 128K x 9
FEBRUARY 11, 2009
SIGNAL DESCRIPTION
INPUTS:
DATA IN (D0 - Dn)
Data inputs for 18-bit wide data (D0-D17) or data inputs for 9-bit wide data
(D0-D8).
CONTROLS:
MASTER RESET (
MRS)
AMasterResetisaccomplishedwheneverthe
MRSinputistakentoaLOW
state.Thisoperationsetstheinternalreadandwritepointerstothefirstlocation
of the RAM array.
PAE will go LOW, PAF will go HIGH, and HF will go HIGH.
IfFWFT/SIisLOWduringMasterResetthentheIDTStandardmode,along
with
EF and FF are selected. EF will go LOW and FF will go HIGH. If FWFT/
SI is HIGH, then the First Word Fall Through mode (FWFT), along with
IRand
OR, are selected. OR will go HIGH and IR will go LOW.
AllcontrolsettingssuchasOW,IW,
BE,RM,PFMandIParedefinedduring
the Master Reset cycle.
DuringaMasterReset,theoutputregisterisinitializedtoallzeroes.AMaster
Reset is required after power up, before a write operation can take place.
MRS
is asynchronous.
See Figure 5, Master Reset Timing, for the relevant timing diagram.
PARTIAL RESET (
PRS)
APartialResetisaccomplishedwheneverthe
PRSinputistakentoaLOW
state. As in the case of the Master Reset, the internal read and write pointers
are set to the first location of the RAM array,
PAEgoesLOW,PAFgoesHIGH,
and
HF goes HIGH.
Whichever mode is active at the time of Partial Reset, IDT Standard mode
or First Word Fall Through, that mode will remain selected. If the IDT Standard
mode is active, then
FFwillgoHIGHandEFwillgoLOW.IftheFirstWordFall
Through mode is active, then
OR will go HIGH, and IR will go LOW.
Following Partial Reset, all values held in the offset registers remain
unchanged. The programming method (parallel or serial) currently active at
the time of Partial Reset is also retained. The output register is initialized to all
zeroes.
PRS is asynchronous.
A Partial Reset is useful for resetting the device during the course of
operation,whenreprogrammingprogrammableflagoffsetsettingsmaynotbe
convenient.
See Figure 6, Partial Reset Timing, for the relevant timing diagram.
ASYNCHRONOUS WRITE (
ASYW)
The write port can be configured for either Synchronous or Asynchronous
mode of operation. If during Master Reset the
ASYW input is LOW, then
Asynchronous operation of the write port will be selected. During Asynchro-
nous operation of the write port the WCLK input becomes WR input, this is the
Asynchronous write strobe input. A rising edge on WR will write data present
on the Dn inputs into the FIFO. (
WEN mustbetiedLOWwhenusingthewrite
port in Asynchronous mode).
When the write port is configured for Asynchronous operation the full flag
(
FF)operatesinanasynchronousmanner,thatis,thefullflagwillbeupdated
based in both a write operation and read operation. Note, if Asynchronous
mode is selected, FWFT is not permissable. Refer to Figures 23, 24, 27 and
28 for relevant timing and operational waveforms.
ASYNCHRONOUS READ (
ASYR)
The read port can be configured for either Synchronous or Asynchronous
mode of operation. If during a Master Reset the
ASYR input is LOW, then
Asynchronousoperationofthereadportwillbeselected.DuringAsynchronous
operation of the read port the RCLK input becomes RD input, this is the
Asynchronous read strobe input. A rising edge on RD will read data from the
FIFO via the output register and Qn port. (
REN must be tied LOW during
Asynchronous operation of the read port).
The
OE input provides three-state control of the Qn output bus, in an
asynchronous manner.
When the read port is configured for Asynchronous operation the device
must be operating on IDT standard mode, FWFT mode is not permissible if the
readportisAsynchronous.TheEmptyFlag(
EF)operatesinanAsynchronous
manner, that is, the empty flag will be updated based on both a read operation
and a write operation. Refer to figures 25, 26, 27 and 28 for relevant timing and
operational waveforms.
RETRANSMIT (
RT)
The Retransmit operation allows data that has already been read to be
accessed again. There are 2 modes of Retransmit operation, normal latency
and zero latency. There are two stages to Retransmit: first, a setup procedure
that resets the read pointer to the first location of memory, then the actual
retransmit, which consists of reading out the memory contents, starting at the
beginning of the memory.
Retransmitsetupisinitiatedbyholding
RTLOWduringarisingRCLKedge.
REN and WEN must be HIGH before bringing RT LOW. When zero latency
is utilized,
REN does not need to be HIGH before bringing RT LOW.
If IDT Standard mode is selected, the FIFO will mark the beginning of the
Retransmitsetupbysetting
EFLOW.Thechangeinlevelwillonlybenoticeable
if
EF was HIGH before setup. During this period, the internal read pointer is
initialized to the first location of the RAM array.
When
EF goesHIGH, Retransmit setupiscompleteand read operations
may begin starting with the first location in memory. Since IDT Standard mode
isselected,everywordreadincludingthefirstwordfollowingRetransmitsetup
requires a LOW on
REN to enable the rising edge of RCLK. See Figure 11,
Retransmit Timing (IDT Standard Mode), for the relevant timing diagram.
IfFWFTmodeisselected,theFIFOwillmarkthebeginningoftheRetransmit
setup by setting
OR HIGH. During this period, the internal read pointer is set
to the first location of the RAM array.
When
ORgoesLOW,Retransmitsetupiscomplete;atthesametime,the
contentsofthefirstlocationappearontheoutputs.SinceFWFTmodeisselected,
the first word appears on the outputs, no LOW on
RENisnecessary.Reading
all subsequent words requires a LOW on
REN to enable the rising edge of
RCLK.SeeFigure12, RetransmitTiming(FWFTMode),fortherelevanttiming
diagram.
In Retransmit operation, zero-latency mode can be selected using the
Retransmit Mode (RM) pin during a Master Reset. This can be applied to both
IDT Standard mode and FWFT mode.
RETRANSMIT LATENCY MODE (RM)
Azero-latencyretransmittimingmodecanbeselectedusingtheRetransmit
timing Mode pin (RM). During Master Reset, a LOW on RM will select zero-
latency retransmit. A HIGH on RM during Master Reset will select normal
latency.
If zero-latency retransmit operation is selected the first data word to be
retransmittedwillbeplacedontheoutputregisterwithrespecttothesameRCLK
edge that initiated the retransmit based on RT being LOW.
Refer to Figure 13 for Retransmit Timing with zero latency (IDT Standard
Mode). Refer to Figure 14 for Retransmit Timing with zero latency (FWFT
Mode).