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72T3695L5BB

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P24P25-P27P28-P30P31-P33P34-P36P37-P39P40-P42P43-P45P46-P48P49-P51P52-P54P55-P57
25
COMMERCIAL AND INDUSTRIAL
TEMPERATURE RANGES
IDT72T3645/55/65/75/85/95/105/115/125 2.5V TeraSync
™™
™™
™ 36-BIT FIFO
1K x 36, 2K x 36, 4K x 36, 8K x 36, 16K x 36, 32K x 36, 64K x 36, 128K x 36 and 256K x 36
FEBRUARY 4, 2009
marked location. During retransmit mode write operations to the device may
continue without hindrance.
FIRST WORD FALL THROUGH/SERIAL IN (FWFT/SI)
This is a dual purpose pin. During Master Reset, the state of the FWFT/
SI input determines whether the device will operate in IDT Standard mode or
First Word Fall Through (FWFT) mode.
If, at the time of Master Reset, FWFT/SI is LOW, then IDT Standard mode
will be selected. This mode uses the Empty Flag (EF) to indicate whether or
not there are any words present in the FIFO memory. It also uses the Full Flag
function (FF) to indicate whether or not the FIFO memory has any free space
for writing. In IDT Standard mode, every word read from the FIFO, including
the first, must be requested using the Read Enable (REN) and RCLK.
If, at the time of Master Reset, FWFT/SI is HIGH, then FWFT mode will be
selected. This mode uses Output Ready (OR) to indicate whether or not there
is valid data at the data outputs (Qn). It also uses Input Ready (IR) to indicate
whether or not the FIFO memory has any free space for writing. In the FWFT
mode, the first word written to an empty FIFO goes directly to Qn after three RCLK
rising edges, REN = LOW is not necessary. Subsequent words must be
accessed using the Read Enable (REN) and RCLK.
After Master Reset, FWFT/SI acts as a serial input for loading PAE and PAF
offsets into the programmable registers. The serial input function can only be
used when the serial loading method has been selected during Master Reset.
Serial programming using the FWFT/SI pin functions the same way in both IDT
Standard and FWFT modes.
WRITE STROBE & WRITE CLOCK (WR/WCLK)
If Synchronous operation of the write port has been selected via ASYW, this
input behaves as WCLK.
A write cycle is initiated on the rising edge of the WCLK input. Data setup
and hold times must be met with respect to the LOW-to-HIGH transition of the
WCLK. It is permissible to stop the WCLK. Note that while WCLK is idle, the FF/
IR, PAF and HF flags will not be updated. (Note that WCLK is only capable of
updating HF flag to LOW). The Write and Read Clocks can either be
independent or coincident.
If Asynchronous operation has been selected this input is WR (write strobe).
Data is Asynchronously written into the FIFO via the Dn inputs whenever there
is a rising edge on WR. In this mode the WEN input must be tied LOW.
WRITE ENABLE (WEN)
When the WEN input is LOW, data may be loaded into the FIFO RAM array
on the rising edge of every WCLK cycle if the device is not full. Data is stored
in the RAM array sequentially and independently of any ongoing read
operation.
When WEN is HIGH, no new data is written in the RAM array on each WCLK
cycle.
To prevent data overflow in the IDT Standard mode, FF will go LOW,
inhibiting further write operations. Upon the completion of a valid read cycle,
FF will go HIGH allowing a write to occur. The FF is updated by two WCLK
cycles + tSKEW after the RCLK cycle.
To prevent data overflow in the FWFT mode, IR will go HIGH, inhibiting
further write operations. Upon the completion of a valid read cycle, IR will go
LOW allowing a write to occur. The IR flag is updated by two WCLK cycles +
tSKEW after the valid RCLK cycle.
WEN is ignored when the FIFO is full in either FWFT or IDT Standard mode.
If Asynchronous operation of the write port has been selected, then WEN
must be held active, (tied LOW).
READ STROBE & READ CLOCK (RD/RCLK)
If Synchronous operation of the read port has been selected via ASYR, this
input behaves as RCLK. A read cycle is initiated on the rising edge of the RCLK
input. Data can be read on the outputs, on the rising edge of the RCLK input.
It is permissible to stop the RCLK. Note that while RCLK is idle, the EF/OR, PAE
and HF flags will not be updated. (Note that RCLK is only capable of updating
the HF flag to HIGH). The Write and Read Clocks can be independent or
coincident.
If Asynchronous operation has been selected this input is RD (Read
Strobe) . Data is Asynchronously read from the FIFO via the output register
whenever there is a rising edge on RD. In this mode the REN and RCS inputs
must be tied LOW. The OE input is used to provide Asynchronous control of the
three-state Qn outputs.
WRITE CHIP SELECT (WCS)
The WCS disables all Write Port inputs (data only) if it is held HIGH. To
perform normal operations on the write port, the WCS must be enabled, held
LOW.
READ ENABLE (REN)
When Read Enable is LOW, data is loaded from the RAM array into the
output register on the rising edge of every RCLK cycle if the device is not empty.
When the REN input is HIGH, the output register holds the previous data
and no new data is loaded into the output register. The data outputs Q0-Qn
maintain the previous data value.
In the IDT Standard mode, every word accessed at Qn, including the first
word written to an empty FIFO, must be requested using REN provided that
RCS is LOW. When the last word has been read from the FIFO, the Empty Flag
(EF) will go LOW, inhibiting further read operations. REN is ignored when the
FIFO is empty. Once a write is performed, EF will go HIGH allowing a read to
occur. The EF flag is updated by two RCLK cycles + tSKEW after the valid WCLK
cycle. Both RCS and REN must be active, LOW for data to be read out on the
rising edge of RCLK.
In the FWFT mode, the first word written to an empty FIFO automatically goes
to the outputs Qn, on the third valid LOW-to-HIGH transition of RCLK + tSKEW
after the first write. REN and RCS do not need to be asserted LOW for the First
Word to fall through to the output register. In order to access all other words,
a read must be executed using REN and RCS. The RCLK LOW-to-HIGH
transition after the last word has been read from the FIFO, Output Ready (OR)
will go HIGH with a true read (RCLK with REN = LOW;RCS = LOW), inhibiting
further read operations. REN is ignored when the FIFO is empty.
If Asynchronous operation of the Read port has been selected, then REN
must be held active, (tied LOW).
SERIAL ENABLE ( SEN )
The SEN input is an enable used only for serial programming of the offset
registers. The serial programming method must be selected during Master
Reset. SEN is always used in conjunction with LD. When these lines are both
LOW, data at the SI input can be loaded into the program register one bit for each
LOW-to-HIGH transition of SCLK.
When SEN is HIGH, the programmable registers retains the previous
settings and no offsets are loaded. SEN functions the same way in both IDT
Standard and FWFT modes.
OUTPUT ENABLE ( OE )
When Output Enable is enabled (LOW), the parallel output buffers receive
data from the output register. When OE is HIGH, the output data bus (Qn) goes
26
COMMERCIAL AND INDUSTRIAL
TEMPERATURE RANGES
IDT72T3645/55/65/75/85/95/105/115/125 2.5V TeraSync
™™
™™
™ 36-BIT FIFO
1K x 36, 2K x 36, 4K x 36, 8K x 36, 16K x 36, 32K x 36, 64K x 36, 128K x 36 and 256K x 36
FEBRUARY 4, 2009
into a high impedance state. During Master or a Partial Reset the OE is the only
input that can place the output bus Qn, into High-Impedance. During Reset the
RCS input can be HIGH or LOW, it has no effect on the Qn outputs.
READ CHIP SELECT ( RCS )
The Read Chip Select input provides synchronous control of the Read
output port. When RCS goes LOW, the next rising edge of RCLK causes the
Qn outputs to go to the Low-Impedance state. When RCS goes HIGH, the next
RCLK rising edge causes the Qn outputs to return to HIGH Z. During a Master
or Partial Reset the RCS input has no effect on the Qn output bus, OE is the only
input that provides High-Impedance control of the Qn outputs. If OE is LOW the
Qn data outputs will be Low-Impedance regardless of RCS until the first rising
edge of RCLK after a Reset is complete. Then if RCS is HIGH the data outputs
will go to High-Impedance.
The RCS input does not effect the operation of the flags. For example, when
the first word is written to an empty FIFO, the EF will still go from LOW to HIGH
based on a rising edge of RCLK, regardless of the state of the RCS input.
Also, when operating the FIFO in FWFT mode the first word written to an
empty FIFO will still be clocked through to the output register based on RCLK,
regardless of the state of RCS. For this reason the user must take care when
a data word is written to an empty FIFO in FWFT mode. If RCS is disabled when
an empty FIFO is written into, the first word will fall through to the output register,
but will not be available on the Qn outputs which are in HIGH-Z. The user must
take RCS active LOW to access this first word, place the output bus in LOW-Z.
REN must remain disabled HIGH for at least one cycle after RCS has gone LOW.
A rising edge of RCLK with RCS and REN active LOW, will read out the next
word. Care must be taken so as not to lose the first word written to an empty
FIFO when RCS is HIGH. Refer to Figure 17, RCS and REN Read Operation
(FWFT Mode). The RCS pin must also be active (LOW) in order to perform
a Retransmit. See Figure 13 for Read Cycle and Read Chip Select Timing (IDT
Standard Mode). See Figure 16 for Read Cycle and Read Chip Select Timing
(First Word Fall Through Mode).
If Asynchronous operation of the Read port has been selected, then RCS
must be held active, (tied LOW). OE provides three-state control of Qn.
WRITE PORT HSTL SELECT (WHSTL)
The control inputs, data inputs and flag outputs associated with the write port
can be setup to be either HSTL or LVTTL. If WHSTL is HIGH during the Master
Reset, then HSTL operation of the write port will be selected. If WHSTL is LOW
at Master Reset, then LVTTL will be selected.
The inputs and outputs associated with the write port are listed in Table 5.
READ PORT HSTL SELECT (RHSTL)
The control inputs, data inputs and flag outputs associated with the read port
can be setup to be either HSTL or LVTTL. If RHSTL is HIGH during the Master
Reset, then HSTL operation of the read port will be selected. If RHSTL is LOW
at Master Reset, then LVTTL will be selected for the read port, then echo clock
and echo read enable will not be provided.
The inputs and outputs associated with the read port are listed in Table 5.
SYSTEM HSTL SELECT (SHSTL)
All inputs not associated with the write and read port can be setup to be either
HSTL or LVTTL. If SHSTL is HIGH during Master Reset, then HSTL operation
of all the inputs not associated with the write and read port will be selected. If
SHSTL is LOW at Master Reset, then LVTTL will be selected. The inputs
associated with SHSTL are listed in Table 5.
LOAD (LD)
This is a dual purpose pin. During Master Reset, the state of the LD input,
along with FSEL0 and FSEL1, determines one of eight default offset values for
the PAE and PAF flags, along with the method by which these offset registers
can be programmed, parallel or serial (see Table 2). After Master Reset, LD
enables write operations to and read operations from the offset registers. Only
the offset loading method currently selected can be used to write to the registers.
Offset registers can be read only in parallel.
After Master Reset, the LD pin is used to activate the programming process
of the flag offset values PAE and PAF. Pulling LD LOW will begin a serial loading
or parallel load or read of these offset values. THIS PIN MUST BE HIGH
AFTER MASTER RESET TO WRITE OR READ DATA TO/FROM THE FIFO
MEMORY.
BUS-MATCHING (BM, IW, OW)
The pins BM, IW and OW are used to define the input and output bus widths.
During Master Reset, the state of these pins is used to configure the device bus
sizes. See Table 1 for control settings. All flags will operate on the word/byte
size boundary as defined by the selection of bus width. See Figure 5 for Bus-
Matching Byte Arrangement.
BIG-ENDIAN/LITTLE-ENDIAN ( BE )
During Master Reset, a LOW on BE will select Big-Endian operation. A
HIGH on BE during Master Reset will select Little-Endian format. This function
is useful when the following input to output bus widths are implemented: x36 to
x18, x36 to x9, x18 to x36 and x9 to x36. If Big-Endian mode is selected, then
the most significant byte (word) of the long word written into the FIFO will be read
out of the FIFO first, followed by the least significant byte. If Little-Endian format
is selected, then the least significant byte of the long word written into the FIFO
will be read out first, followed by the most significant byte. The mode desired
is configured during master reset by the state of the Big-Endian (BE) pin. See
Figure 5 for Bus-Matching Byte Arrangement.
PROGRAMMABLE FLAG MODE (PFM)
During Master Reset, a LOW on PFM will select Asynchronous Program-
mable flag timing mode. A HIGH on PFM will select Synchronous Program-
mable flag timing mode. If asynchronous PAF/PAE configuration is selected
(PFM, LOW during MRS), the PAE is asserted LOW on the LOW-to-HIGH
transition of RCLK. PAE is reset to HIGH on the LOW-to-HIGH transition of
WCLK. Similarly, the PAF is asserted LOW on the LOW-to-HIGH transition of
WCLK and PAF is reset to HIGH on the LOW-to-HIGH transition of RCLK.
If synchronous PAE/PAF configuration is selected (PFM, HIGH during
MRS) , the PAE is asserted and updated on the rising edge of RCLK only and
not WCLK. Similarly, PAF is asserted and updated on the rising edge of WCLK
only and not RCLK. The mode desired is configured during master reset by
the state of the Programmable Flag Mode (PFM) pin.
INTERSPERSED PARITY (IP)
During Master Reset, a LOW on IP will select Non-Interspersed Parity
mode. A HIGH will select Interspersed Parity mode. The IP bit function allows
the user to select the parity bit in the word loaded into the parallel port (D
0-Dn)
when programming the flag offsets. If Interspersed Parity mode is selected, then
the FIFO will assume that the parity bits are located in bit position D8, D17, D26
and D35 during the parallel programming of the flag offsets. If Non-Interspersed
Parity mode is selected, then D8, D17 and D28 are is assumed to be valid bits
and D32, D33, D34 and D35 are ignored. IP mode is selected during Master
Reset by the state of the IP input pin.
27
COMMERCIAL AND INDUSTRIAL
TEMPERATURE RANGES
IDT72T3645/55/65/75/85/95/105/115/125 2.5V TeraSync
™™
™™
™ 36-BIT FIFO
1K x 36, 2K x 36, 4K x 36, 8K x 36, 16K x 36, 32K x 36, 64K x 36, 128K x 36 and 256K x 36
FEBRUARY 4, 2009
OUTPUTS:
FULL FLAG ( FF/IR )
This is a dual purpose pin. In IDT Standard mode, the Full Flag (FF) function
is selected. When the FIFO is full, FF will go LOW, inhibiting further write
operations. When FF is HIGH, the FIFO is not full. If no reads are performed
after a reset (either MRS or PRS), FF will go LOW after D writes to the FIFO
(D = 1,024 for the IDT72T3645, 2,048 for the IDT72T3655, 4,096 for the
IDT72T3665, 8,192 for the IDT72T3675, 16,384 for the IDT72T3685, 32,768
for the IDT72T3695, 65,536 for the IDT72T36105, 131,072 for the IDT72T36115
and 262,144 for the IDT72T36125). See Figure 11, Write Cycle and Full Flag
Timing (IDT Standard Mode), for the relevant timing information.
In FWFT mode, the Input Ready (IR) function is selected. IR goes LOW
when memory space is available for writing in data. When there is no longer
any free space left, IR goes HIGH, inhibiting further write operations. If no reads
are performed after a reset (either MRS or PRS), IR will go HIGH after D writes
to the FIFO (D = 1,025 for the IDT72T3645, 2,049 for the IDT72T3655, 4,097
for the IDT72T3665, 8,193 for the IDT72T3675, 16,385 for the IDT72T3685,
32,769 for the IDT72T3695, 65,537 for the IDT72T36105, 131,073 for the
IDT72T36115 and 262,145 for the IDT72T36125). See Figure 14, Write
Timing (FWFT Mode), for the relevant timing information.
The IR status not only measures the contents of the FIFO memory, but also
counts the presence of a word in the output register. Thus, in FWFT mode, the
total number of writes necessary to deassert IR is one greater than needed to
assert FF in IDT Standard mode.
FF/IR is synchronous and updated on the rising edge of WCLK. FF/IR are
double register-buffered outputs.
Note, when the device is in Retransmit mode, this flag is a comparison of the
write pointer to the ‘marked’ location. This differs from normal mode where this
flag is a comparison of the write pointer to the read pointer.
EMPTY FLAG ( EF/OR )
This is a dual purpose pin. In the IDT Standard mode, the Empty Flag (EF)
function is selected. When the FIFO is empty, EF will go LOW, inhibiting further
read operations. When EF is HIGH, the FIFO is not empty. See Figure 12, Read
Cycle, Empty Flag and First Word Latency Timing (IDT Standard Mode), for
the relevant timing information.
In FWFT mode, the Output Ready (OR) function is selected. OR goes LOW
at the same time that the first word written to an empty FIFO appears valid on
the outputs. OR stays LOW after the RCLK LOW to HIGH transition that shifts
the last word from the FIFO memory to the outputs. OR goes HIGH only with
a true read (RCLK with REN = LOW). The previous data stays at the outputs,
indicating the last word was read. Further data reads are inhibited until OR goes
LOW again. See Figure 15, Read Timing (FWFT Mode), for the relevant timing
information.
EF/OR is synchronous and updated on the rising edge of RCLK.
In IDT Standard mode, EF is a double register-buffered output. In FWFT
mode, OR is a triple register-buffered output.
PROGRAMMABLE ALMOST-FULL FLAG ( PAF )
The Programmable Almost-Full flag (PAF) will go LOW when the FIFO
reaches the almost-full condition. In IDT Standard mode, if no reads are
performed after reset (MRS), PAF will go LOW after (D - m) words are written
to the FIFO. The PAF will go LOW after (1,024-m) writes for the IDT72T3645,
(2,048-m) writes for the IDT72T3655, (4,096-m) writes for the IDT72T3665,
(8,192-m) writes for the IDT72T3675, (16,384-m) writes for the IDT72T3685,
(32,768-m) writes for the IDT72T3695, (65,536-m) writes for the IDT72T36105,
(131,072-m) writes for the IDT72T36115 and (262,144-m) writes for the
IDT72T36125. The offset “m” is the full offset value. The default setting for this
value is stated in the footnote of Table 3.
In FWFT mode, the PAF will go LOW after (1,025-m) writes for the
IDT72T3645, (2,049-m) writes for the IDT72T3655, (4,097-m) writes for the
IDT72T3665 and (8,193-m) writes for the IDT72T3675, (16,385-m) writes for
the IDT72T3685, (32,769-m) writes for the IDT72T3695, (65,537-m) writes for
the IDT72T36105, (131,073-m) writes for the IDT72T36115 and (262,145-m)
writes for the IDT72T36125, where m is the full offset value. The default setting
for this value is stated in Table 4.
See Figure 23, Synchronous Programmable Almost-Full Flag Timing (IDT
Standard and FWFT Mode), for the relevant timing information.
If asynchronous PAF configuration is selected, the PAF is asserted LOW
on the LOW-to-HIGH transition of the Write Clock (WCLK). PAF is reset to HIGH
on the LOW-to-HIGH transition of the Read Clock (RCLK). If synchronous PAF
configuration is selected, the PAF is updated on the rising edge of WCLK. See
Figure 25, Asynchronous Almost-Full Flag Timing (IDT Standard and FWFT
Mode).
Note, when the device is in Retransmit mode, this flag is a comparison of the
write pointer to the ‘marked’ location. This differs from normal mode where this
flag is a comparison of the write pointer to the read pointer.
PROGRAMMABLE ALMOST-EMPTY FLAG ( PAE )
The Programmable Almost-Empty flag (PAE) will go LOW when the FIFO
reaches the almost-empty condition. In IDT Standard mode, PAE will go LOW
when there are n words or less in the FIFO. The offset “n” is the empty offset
value. The default setting for this value is stated in the footnote of Table 1.
In FWFT mode, the PAE will go LOW when there are n+1 words or less
in the FIFO. The default setting for this value is stated in Table 2.
See Figure 24, Synchronous Programmable Almost-Empty Flag Timing
(IDT Standard and FWFT Mode), for the relevant timing information.
If asynchronous PAE configuration is selected, the PAE is asserted LOW
on the LOW-to-HIGH transition of the Read Clock (RCLK). PAE is reset to HIGH
on the LOW-to-HIGH transition of the Write Clock (WCLK). If synchronous PAE
configuration is selected, the PAE is updated on the rising edge of RCLK. See
Figure 26, Asynchronous Programmable Almost-Empty Flag Timing (IDT
Standard and FWFT Mode).
HALF-FULL FLAG ( HF )
This output indicates a half-full FIFO. The rising WCLK edge that fills the FIFO
beyond half-full sets HF LOW. The flag remains LOW until the difference between
the write and read pointers becomes less than or equal to half of the total depth
of the device; the rising RCLK edge that accomplishes this condition sets HF
HIGH.
In IDT Standard mode, if no reads are performed after reset (MRS or PRS),
HF will go LOW after (D/2 + 1) writes to the FIFO, where D = 1,024 for the
IDT72T3645, 2,048 for the IDT72T3655, 4,096 for the IDT72T3665, 8,192
for the IDT72T3675, 16,384 for the IDT72T3685, 32,768 for the IDT72T3695,
65,536 for the IDT72T36105, 131,072 for the IDT72T36115 and 262,144 for
the IDT72T36125.
In FWFT mode, if no reads are performed after reset (MRS or PRS), HF
will go LOW after (D-1/2 + 2) writes to the FIFO, where D = 1,025 for the
IDT72T3645, 2,049 for the IDT72T3655, 4,097 for the IDT72T3665, 8,193 for
the IDT72T3675, 16,385 for the IDT72T3685, 32,769 for the IDT72T3695,
65,537 for the IDT72T36105, 131,073 for the IDT72T36115 and 262,145 for
the IDT72T36125.
See Figure 27, Half-Full Flag Timing (IDT Standard and FWFT Modes),
for the relevant timing information. Because HF is updated by both RCLK and
WCLK, it is considered asynchronous.
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P24P25-P27P28-P30P31-P33P34-P36P37-P39P40-P42P43-P45P46-P48P49-P51P52-P54P55-P57

72T3695L5BB

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FIFO 2.5V 32K X 36 FIFO
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