AL4CS211 datasheet(11/25 Pages) ETC1

11 / 25 page

AL4CS211/AL4CS221/AL4CS231/AL4CS241/AL4CS251

December 14, 2001

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).

AL4CS211 Datasheet(PDF) 11 Page - List of Unclassifed Manufacturers