IDT72261 IDT [Integrated Device Technology], IDT72261 Datasheet - Page 13

• Manufacturer Part Number: IDT72261
• Description: CMOS SUPERSYNC FIFOO 16,384 x 9, 32,768 x 9
• Manufacturer: IDT [Integrated Device Technology]

IDT72261/72271 SyncFIFO
16,384 x 9, 32,768 x 9
LOW, then m = 07FH and the
words from the Full boundary, if
and the
Full boundary.
minus 1 (16,383 words for the 72261, 32,767 words for the
72271) can be programmed into the Full Offset register.
(
IDT72261, and (32,768-m) writes to the IDT72271.
or
IDT72261, and (32,769-m) writes to the IDT72271. In this
case, the first word written to an empty FIFO does not stay in
memory, but goes unrequested to the output register; there-
fore, it has no effect on determining the state of
during the first word latency period (t
data will be ignored until
available at the output port. This is true for both timing modes.
WCLK. It is double-registered to enhance metastable immu-
nity.
PROGRAMMABLE ALMOST-EMPTY FLAG (
when the FIFO reaches the Almost-Empty condition as speci-
fied by the offset n stored in the Empty Offset register.
one of two possible default offset values are chosen. If
LOW, then n = 07FH and the
words from the Empty boundary, if
and the
Empty boundary.
minus 1 (16,383 words for the 72261, 32,767 words for the
72271) can be programmed into the Empty Offset register.
(
MRS
MRS
Any integral value of m from 0 to the maximum FIFO depth
In IDT Standard Mode, if no reads are performed after reset
In FWFT Mode, if no reads are performed after reset (
Note that even though
PAF
The Programmable Almost-Empty Flag (
At the time of Master Reset, depending on the state of
Any integral value of n from 0 to the maximum FIFO depth
In IDT Standard Mode, if no reads are performed after reset
PRS
or
or
),
PAF
PAE
is synchronous and updated on the rising edge of
PRS
PRS
PAF
switching threshold is 1023 words away from the
switching threshold is 1023 words away from the
),
),
PAF
will go LOW after (16,385-m) writes to the
PAE
will go LOW after (16,384-m) writes to the
will go HIGH after (n + 1) writes to the
EF
PAF
goes HIGH indicating that data is
PAE
PAF
is programmed to switch LOW
LD
LD
switching threshold is 127
switching threshold is 127
is HIGH, then m = 3FFH
is HIGH, then n = 3FFH
FWL
), attempts to read
PAE
PAE
PAE
) will go LOW
PAF
)
.
LD
MRS
LD
is
,
IDT72261/72271.
or
72271. In this case, the first word written to an empty FIFO
does not stay in memory, but goes unrequested to the output
register; therefore, it has no effect on determining the state of
PAE
during the first word latency period (t
data will be ignored until
available at the output port. This is true for both timing modes.
RCLK. It is double-registered to enhance metastable immu-
nity.
HALF-FULL FLAG (
edge that fills the memory beyond half-full sets
flag remains LOW until the difference between the write and
read pointers becomes less than or equal to one half of the
total depth of the device, the rising RCLK edge that accom-
plishes this condition also sets
(
is the maximum FIFO depth ( 16,384 words for the IDT72261,
32,768 words for the IDT72271).
or
72271. In this case, the first word written to an empty FIFO
does not stay in memory, but goes unrequested to the output
register; therefore, it has no effect on determining the state of
HF
tion purposes, it is asynchronous.
DATA OUTPUTS (Q
MRS
PRS
PRS
.
In FWFT Mode, if no reads are performed after reset (
Note that even though
PAE
This output indicates a half-full memory. The rising WCLK
In IDT Standard Mode, if no reads are performed after reset
In FWFT Mode, if no reads are performed after reset (
Q
Because
.
0
-Q
or
),
),
is synchronous and updated on the rising edge of
8
PRS
PAE
HF
are data outputs for 9-bit wide data.
MILITARY AND COMMERCIAL TEMPERATURE RANGES
will go LOW after (D/2+2) writes to the IDT72261/
),
HF
will go HIGH after (n+2) writes to the IDT72261/
HF
uses both RCLK and WCLK for synchroniza-
will go LOW after (D/2 + 1) writes, where D
HF HF
0
-Q
)
EF
8
PAE
)
goes HIGH indicating that data is
is programmed to switch HIGH
HF
HIGH.
FWL
), attempts to read
HF
LOW. The
MRS
MRS
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