2.5 VOLT HIGH-SPEED TeraSync
TM
FIFO 72-BIT CONFIGURATIONS
ADVANCE INFORMATION
16,384 x 72, 32,768 x 72,
65,536 x 72, 131,072 x 72
IDT72T7285, IDT72T7295,
IDT72T72105, IDT72T72115
FEATURES:
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Choose among the following memory organizations:
IDT72T7285
16,384 x 72
IDT72T7295
32,768 x 72
IDT72T72105
65,536 x 72
IDT72T72115
131,072 x 72
Up to 200 MHz Operation of Clocks
User selectable HSTL/LVTTL Input and/or Output
Read Enable & Read Clock Echo outputs aid high speed operation
User selectable Asynchronous read and/or write port timing
Mark & Retransmit, resets read pointer to user marked position
Write Chip Select (WCS) input disables Write Port HSTL inputs
Read Chip Select (RCS) synchronous to RCLK
Programmable Almost-Empty and Almost-Full flags, each flag can
default to one of eight preselected offsets
Program programmable flags by either serial or parallel means
Selectable synchronous/asynchronous timing modes for Almost-
Empty and Almost-Full flags
Separate SCLK input for Serial programming of flag offsets
User selectable input and output port bus-sizing
- x72 in to x72 out
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- x72 in to x36 out
- x72 in to x18 out
- x36 in to x72 out
- x18 in to x72 out
Big-Endian/Little-Endian user selectable byte representation
Auto power down minimizes standby power consumption
Master Reset clears entire FIFO
Partial Reset clears data, but retains programmable settings
Empty, Full and Half-Full flags signal FIFO status
Select IDT Standard timing (using
EF
and
FF
flags) or First Word
Fall Through timing (using
OR
and
IR
flags)
Output enable puts data outputs into high impedance state
JTAG port, provided for Boundary Scan function
Available in 324-pin (19mm x 19mm)Plastic Ball Grid Array (PBGA)
Easily expandable in depth and width
Independent Read and Write Clocks (permit reading and writing
simultaneously)
High-performance submicron CMOS technology
Industrial temperature range (–40°C to +85°C) is available
°
°
FUNCTIONAL BLOCK DIAGRAM
D
0
-D
n
(x72, x36 or x18)
WEN
WCLK/WR
WCS
LD
SEN
SCLK
INPUT REGISTER
OFFSET REGISTER
FF/IR
PAF
EF/OR
PAE
HF
FWFT/SI
PFM
FSEL0
FSEL1
ASYW
WRITE CONTROL
LOGIC
WRITE POINTER
BE
IP
BM
IW
OW
MRS
PRS
TCK
TRST
TMS
TDO
TDI
Vref
WHSTL
RHSTL
SHSTL
CONTROL
LOGIC
BUS
CONFIGURATION
RESET
LOGIC
RAM ARRAY
16,384 x 72
32,768 x 72
65,536 x 72
131,072 x 72
FLAG
LOGIC
READ POINTER
OUTPUT REGISTER
READ
CONTROL
LOGIC
RT
MARK
ASYR
JTAG CONTROL
(BOUNDARY SCAN)
RCLK/RD
REN
RCS
HSTL I/0
CONTROL
OE
EREN
5994 drw01
Q
0
-Q
n
(x72, x36 or x18)
ERCLK
The IDT logo is a registered trademark and the TeraSync FIFO is a trademark of Integrated Device Technology, Inc.
COMMERCIAL AND INDUSTRIAL TEMPERATURE RANGES
1
©
2001 Integrated Device Technology, Inc.
MAY 2001
DSC-5994/1
IDT72T7285/95/105/115 2.5V TeraSync 72-BIT FIFO
16,384 x 72, 32,768 x 72, 65,536 x 72, 131,072 x 72
COMMERCIAL AND INDUSTRIAL
TEMPERATURE RANGES
DESCRIPTION:
The IDT72T7285/72T7295/72T72105/72T72115 are exceptionally deep,
extrememly high speed, CMOS First-In-First-Out (FIFO) memories with
clocked read and write controls and a flexible Bus-Matching x72/x36/x18 data
flow. These FIFOs offer several key user benefits:
• Flexible x72/x36/x18 Bus-Matching on both read and write ports
• A user selectable MARK location for retransmit
• User selectable I/O structure for HSTL or LVTTL
• Asynchronous/Synchronous translation on the read or write ports
• The first word data latency period, from the time the first word is written to an
empty FIFO to the time it can be read, is fixed and short.
• High density offerings up to 9 Mbit
Bus-Matching TeraSync FIFOs are particularly appropriate for network,
video, telecommunications, data communications and other applications that
need to buffer large amounts of data and match busses of unequal sizes.
Each FIFO has a data input port (D
n
) and a data output port (Q
n
), both of
which can assume either a 72-bit, 36-bit or a 18-bit width as determined by the
state of external control pins Input Width (IW), Output Width (OW), and Bus-
Matching (BM) pin during the Master Reset cycle.
The input port can be selected as either a Synchronous (clocked) interface,
or Asynchronous interface. During Synchronous operation the input port is
controlled by a Write Clock (WCLK) input and a Write Enable (WEN) input. Data
present on the Dn data inputs is written into the FIFO on every rising edge of
WCLK when
WEN
is asserted. During Asynchronous operation only the WR
input is used to write data into the FIFO. Data is written on a rising edge of WR,
the
WEN
input should be tied to its active state, (LOW).
The input port can be selected for either 2.5V LVTTL or HSTL operation,
this operation is selected by the state of the WHSTL input during a master reset.
A Write Chip Select input (WCS) is provided for use when the write port is in
HSTL mode. During HSTL operation the
WCS
input can be used to disable write
port inputs (data only).
The output port can be selected as either a Synchronous (clocked) interface,
or Asynchronous interface. During Synchronous operation the output port is
controlled by a Read Clock (RCLK) input and Read Enable (REN) input. Data
is read from the FIFO on every rising edge of RCLK when
REN
is asserted.
During Asynchronous operation only the RD input is used to read data from the
FIFO. Data is read on a rising edge of RD, the
REN
input should be tied to its
active state, LOW. When Asynchronous operation is selected on the output port
the FIFO must be configured for Standard IDT mode, also the
RCS
should be
tied LOW and the
OE
input used to provide three-state control of the outputs, Qn.
The output port can be selected for either 2.5V LVTTL or HSTL operation,
this operation is selected by the state of the RHSTL input during a master reset.
An Output Enable (OE) input is provided for three-state control of the outputs.
A Read Chip Select (RCS) input is also provided, the
RCS
input is synchronized
to the read clock, and also provides three-state control of the Qn data outputs.
When
RCS
is disabled, the data outputs will be high impedance. During
Asynchronous operation of the output port,
RCS
should be enabled, held LOW.
Echo Read Enable,
EREN
and Echo Read Clock, ERCLK outputs are
provided. These are outputs from the read port of the FIFO that are required
for high speed data communication, to provide tighter synchronization between
the data being transmitted from the Qn outputs and the data being received by
the input device. Data read from the read port is available on the output bus with
respect to
EREN
and ERCLK, this is very useful when data is being read at
high speed. The ERCLK and
EREN
outputs are non-functional when the Read
port is setup for Asynchronous mode.
The frequencies of both the RCLK and the WCLK signals may vary from 0
to f
MAX
with complete independence. There are no restrictions on the frequency
of the one clock input with respect to the other.
There are two possible timing modes of operation with these devices: IDT
Standard mode and First Word Fall Through (FWFT) mode.
In
IDT Standard mode,
the first word written to an empty FIFO will not appear
on the data output lines unless a specific read operation is performed. A read
operation, which consists of activating
REN
and enabling a rising RCLK edge,
will shift the word from internal memory to the data output lines.
In
FWFT mode,
the first word written to an empty FIFO is clocked directly
to the data output lines after three transitions of the RCLK signal. A
REN
does
not have to be asserted for accessing the first word. However, subsequent
words written to the FIFO do require a LOW on
REN
for access. The state of
the FWFT/SI input during Master Reset determines the timing mode in use.
For applications requiring more data storage capacity than a single FIFO
can provide, the FWFT timing mode permits depth expansion by chaining FIFOs
in series (i.e. the data outputs of one FIFO are connected to the corresponding
data inputs of the next). No external logic is required.
These FIFOs have five flag pins,
EF/OR
(Empty Flag or Output Ready),
FF/IR
(Full Flag or Input Ready),
HF
(Half-full Flag),
PAE
(Programmable
Almost-Empty flag) and
PAF
(Programmable Almost-Full flag). The
EF
and
FF
functions are selected in IDT Standard mode. The
IR
and
OR
functions are
selected in FWFT mode.
HF, PAE
and
PAF
are always available for use,
irrespective of timing mode.
PAE
and
PAF
can be programmed independently to switch at any point in
memory. Programmable offsets determine the flag switching threshold and can
be loaded by two methods: parallel or serial. Eight default offset settings are also
provided, so that
PAE
can be set to switch at a predefined number of locations
from the empty boundary and the
PAF
threshold can also be set at similar
predefined values from the full boundary. The default offset values are set during
Master Reset by the state of the FSEL0, FSEL1, and
LD
pins.
For serial programming,
SEN
together with
LD
on each rising edge of
SCLK, are used to load the offset registers via the Serial Input (SI). For parallel
programming,
WEN
together with
LD
on each rising edge of WCLK, are used
to load the offset registers via D
n
.
REN
together with
LD
on each rising edge
of RCLK can be used to read the offsets in parallel from Q
n
regardless of whether
serial or parallel offset loading has been selected.
During Master Reset (MRS) the following events occur: the read and write
pointers are set to the first location of the FIFO. The FWFT pin selects IDT
Standard mode or FWFT mode.
The Partial Reset (PRS) also sets the read and write pointers to the first
location of the memory. However, the timing mode, programmable flag
programming method, and default or programmed offset settings existing before
Partial Reset remain unchanged. The flags are updated according to the timing
mode and offsets in effect.
PRS
is useful for resetting a device in mid-operation,
when reprogramming programmable flags would be undesirable.
It is also possible to select the timing mode of the
PAE
(Programmable Almost-
Empty flag) and
PAF
(Programmable Almost-Full flag) outputs. The timing
modes can be set to be either asynchronous or synchronous for the
PAE
and
PAF
flags.
If asynchronous
PAE/PAF
configuration is selected, 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.
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IDT72T7285/95/105/115 2.5V TeraSync 72-BIT FIFO
16,384 x 72, 32,768 x 72, 65,536 x 72, 131,072 x 72
COMMERCIAL AND INDUSTRIAL
TEMPERATURE RANGES
DESCRIPTION (CONTINUED)
If synchronous
PAE/PAF
configuration is selected , 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 MasterReset by the state of the Programmable Flag
Mode (PFM) pin.
This device includes a Retransmit from Mark feature that utilizes two control
inputs, MARK and ,
RT
(Retransmit). If the MARK input is enabled with respect
to the RCLK, the memory location being read at that point will be marked. Any
subsequent retransmit operation,
RT
goes LOW, will reset the read pointer to
this ‘marked’ location.
The device can be configured with different input and output bus widths as
shown in Table 1.
A Big-Endian/Little-Endian data word format is provided. This function is
useful when data is written into the FIFO in long word format (x36/x18) and read
out of the FIFO in small word (x18/x9) format. 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.
The Interspersed/Non-Interspersed Parity (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 bit is located in bit positions D8, D17, D26 and
D35 during the parallel programming of the flag offsets. If Non-Interspersed
Parity mode is selected, then D8 and D17 are assumed to be valid bits. IP mode
is selected during Master Reset by the state of the IP input pin.
If, at any time, the FIFO is not actively performing an operation, the chip will
automatically power down. Once in the power down state, the standby supply
current consumption is minimized. Initiating any operation (by activating control
inputs) will immediately take the device out of the power down state.
Both an Asynchronous Output Enable pin (OE) and Synchronous Read
Chip Select pin (RCS) are provided on the FIFO. The Synchronous Read Chip
Select is synchronized to the RCLK. Both the output enable and read chip select
control the output buffer of the FIFO, causing the buffer to be either HIGH
impedance or LOW impedance.
A JTAG test port is provided, here the FIFO has fully functional Boundary
Scan feature, compliant with IEEE 1449.1 Standard Test Access Port and
Boundary Scan Architecture.
The TeraSync FIFO has the capability of operating its ports (write and/or
read) in either LVTTL or HSTL mode, each ports selection independent of the
other. The write port selection is made via WHSTL and the read port selection
via RHSTL. An additional input SHSTL is also provided, this allows the user
to select HSTL operation for other pins on the device (not associated with the
write or read ports).
The IDT72T7285/72T7295/72T72105/72T72115 are fabricated using
IDT’s high speed submicron CMOS technology.
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