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IDT72V3690L7.5PFI

3.3 VOLT HIGH-DENSITY SUPERSYNC™ II 36-BIT FIFO

Integrated Device Technology 

IDT72V3640/50/60/70/80/90/110 3.3V HIGH DENSITY SUPERSYNC IITM 36-BIT FIFO

1,024 x 36, 2,048 x 36, 4,096 x 36, 8,192 x 36, 16,384 x 36, 32,768 x 36, 65,536 x 36, 131,072 x 36

COMMERCIAL AND INDUSTRIAL

TEMPERATURE RANGES

FUNCTIONAL DESCRIPTION

TIMING MODES: IDT STANDARD vs FIRST WORD FALL THROUGH

(FWFT) MODE

The IDT72V3640/72V3650/72V3660/72V3670/72V3680/72V3690/

72V36100/72V36110 support two different timing modes of operation: IDT

Standard mode or First Word Fall Through (FWFT) mode. The selection of

which mode will operate is determined during Master Reset, by the state of the

FWFT/SI input.

If, at the time of Master Reset, FWFT/SI is LOW, then IDT Standard mode

will be selected. This mode uses the Empty Flag (EF) to indicate whether or

not there are any words present in the FIFO. It also uses the Full Flag function

(FF) to indicate whether or not the FIFO has any free space for writing. In IDT

Standard mode, every word read from the FIFO, including the first, must be

requested using the Read Enable (REN) and RCLK.

If, at the time of Master Reset, FWFT/SI is HIGH, then FWFT mode will be

selected. This mode uses Output Ready (OR) to indicate whether or not there

is valid data at the data outputs (Qn). It also uses Input Ready (IR) to indicate

whether or not the FIFO has any free space for writing. In the FWFT mode,

the first word written to an empty FIFO goes directly to Qn after three RCLK rising

edges, REN = LOW is not necessary. Subsequent words must be accessed

using the Read Enable (REN) and RCLK.

Various signals, both input and output signals operate differently depending

on which timing mode is in effect.

IDT STANDARD MODE

In this mode, the status flags, FF, PAF, HF, PAE, and EF operate in the

manner outlined in Table 3. To write data into to the FIFO, Write Enable (WEN)

must be LOW. Data presented to the DATA IN lines will be clocked into the FIFO

on subsequent transitions of the Write Clock (WCLK). After the first write is

performed, the Empty Flag (EF) will go HIGH. Subsequent writes will continue

to fill up the FIFO. The Programmable Almost-Empty flag (PAE) will go HIGH

after n + 1 words have been loaded into the FIFO, where n is the empty offset

value. The default setting for these values are stated in the footnote of Table 2.

This parameter is also user programmable. See section on Programmable Flag

Offset Loading.

If one continued to write data into the FIFO, and we assumed no read

operations were taking place, the Half-Full flag (HF) would toggle to LOW once

the 513rd word for IDT72V3640, 1,025th word for IDT72V3650, 2,049th word

for IDT72V3660, 4,097th word for IDT72V3670, 8,193th word for the

IDT72V3680, 16,385th word for the IDT72V3690, 32,769th word for the

IDT72V36100 and 65,537th word for the IDT72V36110, respectively was

written into the FIFO. Continuing to write data into the FIFO will cause the

Programmable Almost-Full flag (PAF) to go LOW. Again, if no reads are

performed, the PAF will go LOW after (1,024-m) writes for the IDT72V3640,

(2,048-m) writes for the IDT72V3650, (4,096-m) writes for the IDT72V3660,

(8,192-m) writes for the IDT72V3670, (16,384-m) writes for the IDT72V3680,

(32,768-m) writes for the IDT72V3690, (65,536-m) writes for the IDT72V36100

and (131,072-m) writes for the IDT72V36110. The offset “m” is the full offset

value. The default setting for these values are stated in the footnote of Table 2.

This parameter is also user programmable. See section on Programmable Flag

Offset Loading.

When the FIFO is full, the Full Flag (FF) will go LOW, inhibiting further write

operations. If no reads are performed after a reset, FF will go LOW after D writes

to the FIFO. D = 1,024 writes for the IDT72V3640, 2,048 writes for the

IDT72V3650, 4,096 writes for the IDT72V3660, 8,192 writes for the IDT72V3670,

16,384 writes for the IDT72V3680, 32,768 writes for the IDT72V3690, 65,536

writes for the IDT72V36100 and 131,072 writes for the IDT72V36110,

respectively.

If the FIFO is full, the first read operation will cause FF to go HIGH.

Subsequent read operations will cause PAF and HF to go HIGH at the conditions

described in Table 3. If further read operations occur, without write operations,

PAE will go LOW when there are n words in the FIFO, where n is the empty

offset value. Continuing read operations will cause the FIFO to become empty.

When the last word has been read from the FIFO, the EF will go LOW inhibiting

further read operations. REN is ignored when the FIFO is empty.

When configured in IDT Standard mode, the EF and FF outputs are double

register-buffered outputs.

Relevant timing diagrams for IDT Standard mode can be found in Figure

7,8,11 and 13.

FIRST WORD FALL THROUGH MODE (FWFT)

In this mode, the status flags, IR, PAF, HF, PAE, and OR operate in the

manner outlined in Table 4. To write data into to the FIFO, WEN must be LOW.

Data presented to the DATA IN lines will be clocked into the FIFO on subsequent

transitions of WCLK. After the first write is performed, the Output Ready (OR)

flag will go LOW. Subsequent writes will continue to fill up the FIFO. PAE will go

HIGH after n + 2 words have been loaded into the FIFO, where n is the empty

offset value. The default setting for these values are stated in the footnote of Table

2. This parameter is also user programmable. See section on Programmable

Flag Offset Loading.

If one continued to write data into the FIFO, and we assumed no read

operations were taking place, the HF would toggle to LOW once the 514th word

for the IDT72V3640, 1,026th word for the IDT72V3650, 2,050th word for the

IDT72V3660, 4,098th word for the IDT72V3670, 8,194th word for the

IDT72V3680, 16,386th word for the IDT72V3690, 32,770th word for the

IDT72V36100 and 65,538th word for the IDT72V36110, respectively was

written into the FIFO. Continuing to write data into the FIFO will cause the PAF

to go LOW. Again, if no reads are performed, the PAF will goLOW after (1,025-m)

writes for the IDT72V3640, (2,049-m) writes for the IDT72V3650, (4,097-m)

writes for the IDT72V3660 and (8,193-m) writes for the IDT72V3670, 16,385

writes for the IDT72V3680, 32,769 writes for the IDT72V3690, 65,537 writes

for the IDT72V36100 and 131,073 writes for the IDT72V36110, where m is the

full offset value. The default setting for these values are stated in the footnote

of Table 2.

When the FIFO is full, the Input Ready (IR) flag will go HIGH, inhibiting further

write operations. If no reads are performed after a reset, IR will go HIGH after

D writes to the FIFO. D = 1,025 writes for the IDT72V3640, 2,049 writes for

the IDT72V3650, 4,097 writes for the IDT72V3660 and 8,193 writes for the

IDT72V3670,16,385 writes for the IDT72V3680, 32,769 writes for the

IDT72V3690, 65,537 writes for the IDT72V36100 and 131,073 writes for the

IDT72V36110, respectively. Note that the additional word in FWFT mode is due

to the capacity of the memory plus output register.

If the FIFO is full, the first read operation will cause the IR flag to go LOW.

Subsequent read operations will cause the PAF and HF to go HIGH at the

conditions described in Table 4. If further read operations occur, without write

operations, the PAE will go LOW when there are n + 1 words in the FIFO, where

n is the empty offset value. Continuing read operations will cause the FIFO to

become empty. When the last word has been read from the FIFO, OR will go

HIGH inhibiting further read operations. REN is ignored when the FIFO is empty.

When configured in FWFT mode, the OR flag output is triple register-

buffered, and the IR flag output is double register-buffered.

Relevant timing diagrams for FWFT mode can be found in Figure 9, 10, 12,

and 14.

9

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