5.14

2

IDT72251 CMOS SyncFIFO

™

8192 x 9

COMMERCIAL TEMPERATURE RANGES

PIN CONFIGURATION

PIN DESCRIPTIONS

Symbol

Name

I/O

Description

Data Inputs

I

Data inputs for a 9-bit bus.

RS

Reset

I

When

RS is set LOW, internal read and write pointers are set to the first location of the RAM array,

FF and PAF go HIGH, and PAE and EF go LOW. A reset is required before an initial WRITE after

power-up.

WCLK

Write Clock

I

Data is written into the FIFO on a LOW-to-HIGH transition of WCLK when the Write

Enable(s) are asserted.

WEN1

Write Enable 1

I

If the FIFO is configured to have programmable flags,

WEN1 is the only write enable pin.

When

WEN1 is LOW, data is written into the FIFO on every LOW-to-HIGH transition WCLK. If

the FIFO is configured to have two write enables,

WEN1 must be LOW and WEN2 must be

HIGH to write data into the FIFO. Data will not be written into the FIFO if the

FF is LOW.

WEN2/

LD Write Enable 2/

I

The FIFO is configured at reset to have either two write enables or programmable flags. If WEN2/

Load

LD is HIGH at reset, this pin operates as a second write enable. If WEN2/LD is LOW at reset,

this pin operates as a control to load and read the programmable flag offsets. If the FIFO is

configured to have two write enables,

WEN1 must be LOW and WEN2 must be HIGH to write

data into the FIFO. Data will not be written into the FIFO if the

FF is LOW. If the FIFO is config-

ured to have programmable flags, WEN2/

LD is held LOW to write or read the programmable flag

offsets.

Data Outputs

O

Data outputs for a 9-bit bus.

RCLK

Read Clock

I

Data is read from the FIFO on a LOW-to-HIGH transition of RCLK when

REN1 and REN2 are

asserted.

REN1

Read Enable 1

I

When

REN1 and REN2 are LOW, data is read from the FIFO on every LOW-to-HIGH transition

of RCLK. Data will not be read from the FIFO if the

EF is LOW.

REN2

Read Enable 2

I

When

REN1 and REN2 are LOW, data is read from the FIFO on every LOW-to-HIGH transition

of RCLK. Data will not be read from the FIFO if the

EF is LOW.

OE

Output Enable

I

When

OE is LOW, the data output bus is active. If OE is HIGH, the output data bus will be in a

high-impedance state.

EF

Empty Flag

O

When

EF is LOW, the FIFO is empty and further data reads from the output are inhibited. When

EF is HIGH, the FIFO is not empty. EF is synchronized to RCLK.

PAE

Programmable

O

When

PAE is LOW, the FIFO is almost empty based on the offset programmed into the FIFO.

Almost-Empty

The default offset at reset is Empty+7.

PAE is synchronized to RCLK.

Flag

PAF

Programmable

O

When

PAF is LOW, the FIFO is almost full based on the offset programmed into the FIFO. The

Almost-Full Flag

default offset at reset is Full-7.

PAF is synchronized to WCLK.

FF

Full Flag

O

When

FF is LOW, the FIFO is full and further data writes into the input are inhibited. When FF is

HIGH, the FIFO is not full.

FF is synchronized to WCLK.

Power

One +5 volt power supply pin.

GND

Ground

One 0 volt ground pin.

2655 tbl 01

PLCC

TOP VIEW

RS

WEN1

WCLK

WEN2/LD

V

Q

Q

Q

Q

5

6

7

8

9

10

11

12

13

CC

8

7

6

5

1

D

0

PAF

PAE

GND

REN1

RCLK

REN2

OE

D

27

26

25

24

23

22

21

29

28

432

1

32 31 30

14 15 16 17 18 19 20

J32-1

INDEX

2655 drw 02b