5.09

2

MILITARY AND COMMERCIAL TEMPERATURE RANGES

IDT72021, IDT72031, IDT72041

CMOS ASYNCHRONOUS FIFO WITH RETRANSMIT 1K x 9, 2K x 9, 4K x 9

PIN CONFIGURATIONS

PIN DESCRIPTIONS

Symbol

Name

I/O

Description

Inputs

I

Data inputs for 9-bit wide data.

RS

Reset

I

When

RS is set LOW, internal READ and WRITE pointers are set to the first location of the RAM

array.

HF and FF go HIGH, and AEF and EF go LOW. A reset is required before an initial WRITE

after power-up.

R and W must be HIGH during RS cycle.

W

Write

I

When WRITE is LOW, data can be written into the RAM array sequentially, independent of

READ. In order for WRITE to be active,

FF must be HIGH. When the FIFO is full (FF-LOW),

the internal WRITE operation is blocked.

R

Read

I

When READ is LOW, data can be read from the RAM array sequentially, independent of

WRITE. In order for READ to be active,

EF must be HIGH. When the FIFO is empty (EF-LOW),

the internal READ operation is blocked. The three-state output buffer is controlled by the read

signal and the external output control

(OE).

FL/RT

First Load/

I

This is a dual-purpose input. In the single device configuration (

XI grounded), activating

retransmit (

FL/RT-LOW) will set the internal READ pointer to the first location. There is no effect

on the WRITE pointer.

R and W must be HIGH before setting FL/RT LOW. Retransmit is not

compatible with depth expansion. In the depth expansion configuration,

FL/RT-LOW indicates

the first activated device.

XI

Expansion In

I

In the single device configuration,

XI is grounded. In depth expansion or daisy chain expansion,

XI is connected to XO (expansion out) of the previous device.

OE

Output Enable

I

When

OE is set HIGH, the data flow through the three-state output buffer is inhibited regardless

of an active READ operation. A read operation does increment the read pointer in this situation.

When

R and OE should be asserted

LOW.

FF

Full Flag

O

When

FF goes LOW, the device is full and further WRITE operations are inhibited. When FF

is HIGH, the device is not full.

EF

Empty Flag

O

When

EF goes LOW, the device is empty and further READ operations are inhibited. When EF

is HIGH, the device is not empty.

AEF

Almost-Empty/

O

When

AEF is LOW, the device is empty to 1/8 full or 7/8 to completely full. When AEF is HIGH,

the device is greater than 1/8 full, but less than 7/8 full.

XO/HF

Expansion Out/

O

This is a dual purpose output. In the single device configuration (

XI grounded), the device is

more than half full when

HF is LOW. In the depth expansion configuration (XO connected to

XI of the next device), a pulse is sent from XO to XI when the last location in the RAM array is

filled.

Outputs

O

Data outputs for 9-bit wide data.

Retransmit

Almost-Full Flag

Half-Full Flag

2677 tbl 01

PLCC TOP VIEW

DIP TOP VIEW

5

6

7

XI

8

AEF

9

FF

10

11

12

13

FL/RT

RS

OE

EF

XO/HF

29

28

27

26

25

24

23

22

21

4

3

2

1

32 31 30

14 15 16 17 18 19 20

INDEX

J32-1

2677 drw 03

FL/RT

RS

OE

XO/HF

EF

R

GND

W

XI

AEF

FF

GND

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

32

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

D32-1

2677 drw 02