IDT72T36115 Integrated Device Technology, IDT72T36115 Datasheet - Page 27

• Manufacturer Part Number: IDT72T36115
• Description: 128k X 36 Terasync Fifo, 2.5v - Best Value!
• Manufacturer: Integrated Device Technology

OUTPUTS:
FULL FLAG ( FF/IR )
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.
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.
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.
double register-buffered outputs.
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 )
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.
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.
mode, OR is a triple register-buffered output.
PROGRAMMABLE ALMOST-FULL FLAG ( PAF )
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
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
In IDT Standard mode, EF is a double register-buffered output. In FWFT
This is a dual purpose pin. In IDT Standard mode, the Full Flag (FF) function
In FWFT mode, the Input Ready (IR) function is selected. IR goes LOW
The IR status not only measures the contents of the FIFO memory, but also
FF/IR is synchronous and updated on the rising edge of WCLK. FF/IR are
Note, when the device is in Retransmit mode, this flag is a comparison of the
This is a dual purpose pin. In the IDT Standard mode, the Empty Flag (EF)
In FWFT mode, the Output Ready (OR) function is selected. OR goes LOW
The Programmable Almost-Full flag (PAF) will go LOW when the FIFO
EF/OR is synchronous and updated on the rising edge of RCLK.
27
IDT72T36125. The offset “m” is the full offset value. The default setting for this
value is stated in the footnote of Table 3.
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.
Standard and FWFT Mode), for the relevant timing information.
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).
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 )
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 the FIFO. The default setting for this value is stated in Table 2.
(IDT Standard and FWFT Mode), for the relevant timing information.
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 )
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.
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.
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.
for the relevant timing information. Because HF is updated by both RCLK and
WCLK, it is considered asynchronous.
In FWFT mode, the PAF will go LOW after (1,025-m) writes for the
See Figure 23, Synchronous Programmable Almost-Full Flag Timing (IDT
See Figure 24, Synchronous Programmable Almost-Empty Flag Timing
If asynchronous PAF configuration is selected, the PAF is asserted LOW
Note, when the device is in Retransmit mode, this flag is a comparison of the
The Programmable Almost-Empty flag (PAE) will go LOW when the FIFO
In FWFT mode, the PAE will go LOW when there are n+1 words or less
If asynchronous PAE configuration is selected, the PAE is asserted LOW
This output indicates a half-full FIFO. The rising WCLK edge that fills the FIFO
In IDT Standard mode, if no reads are performed after reset (MRS or PRS),
In FWFT mode, if no reads are performed after reset (MRS or PRS), HF
See Figure 27, Half-Full Flag Timing (IDT Standard and FWFT Modes),
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