AL4CS241 AverLogic Technologies, Inc., AL4CS241 Datasheet - Page 11

• Manufacturer Part Number: AL4CS241
• Manufacturer: AverLogic Technologies, Inc.

AL4CS211/AL4CS221/AL4CS231/AL4CS241/AL4CS251
However, writing all offset registers does not have to occur consecutively. The FIFO can return to
normal read/write operation by bringing the Write Enable 2<Load> (WEN2</LD>) pin HIGH after
one or two offset registers can be written. When the Write Enable 2/Load (WEN2/LD) pin is set
LOW again, and Write Enable 1 (/WEN1) is LOW, the next offset register in sequence is written. The
contents of the offset registers can be read on the output lines when the Write Enable 2<Load>
(WEN2</LD>) pin is set low and both Read Enables (/REN1, /REN2) are LOW. Data can be read on
the rising edge of the Read Clock (RCLK). A read and write to the offset registers should not be
performed simultaneously.
8.3 Flags
8.3.1 Full Flag (/FF)
The Full Flag (/FF) will go LOW, inhibiting further write operation, when the device is full. If no
reads are performed after Reset (/RS), the Full Flag (/FF) will go LOW after 512 writes for the
AL4CS211, 1,024 writes for the AL4CS221, 2,048 writes for the AL4CS231, 4,096 writes for the
AL4CS241 and 8,192 writes for the AL4CS251. The Full Flag (/FF) is synchronized with respect to
the rising edge of the Write Clock (WCLK).
8.3.2 Empty Flag (/EF)
The Empty Flag (/EF) will go LOW, inhibiting further read operations, when the read pointer is equal
to the write pointer, indicating the device is empty. The Empty Flag (/EF) is synchronized with
respect to the rising edge of the Read Clock (RCLK).
8.3.3 Programmable Almost- Full Flag (/PAF)
The Programmable Almost-Full flag (/PAF) will go LOW when the FIFO reaches the almost-full
condition. If no reads are performed after Reset (/RS), the Programmable Almost-Full flag (/PAF)
will go LOW after (512-m) writes for the AL4CS211, (1,024-m) writes for the AL4CS221, (2,048-m)
writes for the AL4CS231, (4,096-m) writes for the AL4CS241 and (8,192-m) writes for the
AL4CS251. The offset “m” is defined in the Full Offset registers. If there is no full offset specified,
the Programmable Almost-Full flag (/PAF) will go LOW at Full-7 words. The Programmable Almost-
Full flag (/PAF) is synchronized with respect to the rising edge of the Write Clock (WCLK).
8.3.4 Programmable Almost-Empty Flag (/PAE)
The Programmable Almost-Empty flag (/PAE) will go LOW when the read pointer is "n+1" locations
less than the write pointer. The offset "n" is defined in the Empty Offset registers. If no reads are
performed after Reset the Programmable Almost-Empty flag (/PAE) will go HIGH after "n+1" for the
AL4CS211/221/231/241/251. If there is no empty offset specified, the Programmable Almost-Empty
flag (/PAE) will go LOW at Empty+7 words. The Programmable Almost-Empty flag (/PAE) is
synchronized with respect to the rising edge of the Read Clock (RCLK).
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AL4CS211/AL4CS221/AL4CS231/AL4CS241/AL4CS251
December 14, 2001