COMMERCIAL AND INDUSTRIAL

TEMPERATURE RANGES

IDT72V261LA/72V271LA

3.3 VOLT CMOS SuperSync FIFO™ 16,384 x 9 and 32,768 x 9

8

IDT72V271LA

IDT72V271LA

FF PAF

HF PAE EF

00

L

H

H

L

H

LH

H

L

L

(n + 2) to 8,193

(n + 2) to 16,385

L

H

H

H

L

LH

L

H

L

(16,385-m) to 16,384

L

L

L

H

L

16,385

32,769

H

L

L

H

L

IDT72V261LA

IDT72V261LA

FF PAF

HF PAE EF

00

H

H

H

L

L

HH

H

L

H

(n + 1) to 8,192

(n + 1) to 16,384

H

H

H

H

H

8,193 to (16,384-(m+1))

16,385 to (32,768-(m+1))

HH

L

H

H

H

L

L

H

H

16,384

32,768

L

L

L

H

H

NOTES:

1. n = Empty Offset, Default Values: n = 127 when parallel offset loading is selected or n = 1,023 when serial offset loading is selected.

2. m = Full Offset, Default Values: m = 127 when parallel offset loading is selected or m = 1,023 when serial offset loading is selected.

NOTES:

1. n = Empty Offset, Default Values: n = 127 when parallel offset loading is selected or n = 1,023 when serial offset loading is selected.

2. m = Full Offset, Default Values: m = 127 when parallel offset loading is selected or m = 1,023 when serial offset loading is selected.

PROGRAMMING FLAG OFFSETS

Full and Empty Flag offset values are user programmable. The

IDT72V261LA/72V271LA has internal registers for these offsets. De-

fault settings are stated in the footnotes of Table 1 and Table 2. Offset

values can be programmed into the FIFO in one of two ways; serial or

parallel loading method. The selection of the loading method is done

using the LD (Load) pin. During Master Reset, the state of the LD input

determines whether serial or parallel flag offset programming is en-

abled. A HIGH on LD during Master Reset selects serial loading of

offset values and in addition, sets a default PAE offset value of 3FFH (a

threshold 1,023 words from the empty boundary), and a default PAF

offset value of 3FFH (a threshold 1,023 words from the full boundary).

A LOW on LD during Master Reset selects parallel loading of offset

values, and in addition, sets a default PAE offset value of 07FH (a

threshold 127 words from the empty boundary), and a default PAF

offset value of 07FH (a threshold 127 words from the full boundary).

See Figure 3, Offset Register Location and Default Values.

In addition to loading offset values into the FIFO, it also possible to read

the current offset values. It is only possible to read offset values via parallel

read.

Figure 4, Programmable Flag Offset Programming Sequence, summa-

rizes the control pins and sequence for both serial and parallel program-

ming modes. For a more detailed description, see discussion that follows.

The offset registers may be programmed (and reprogrammed) any time

after Master Reset, regardless of whether serial or parallel programming

has been selected.

TABLE 1 — STATUS FLAGS FOR IDT STANDARD MODE

TABLE 2 — STATUS FLAGS FOR FWFT MODE

Number of

Words in

FIFO

Number of

Words in