5.34

2

IDT72131, IDT72141

CMOS PARALLEL-TO-SERIAL FIFO 2048 x 9 & 4096 x 9

COMMERCIAL TEMPERATURE RANGES

Retransmit

Clock

Expansion

STATUS FLAGS

Number of Words in FIFO

IDT72131

IDT72141

FF

AEF

HF

EF

00

H

L

H

L

1-255

1-511

H

L

H

H

256-1024

512-2048

H

H

H

H

1025-1792

2049-3584

H

H

L

H

1793-2047

3585-4095

H

L

L

H

2048

4096

L

L

L

H

2751 tbl 02

Almost-Full Flag

Half-Full Flag

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.

W must be HIGH and SOCP must be LOW during RS cycle.

W

Write

I

A write cycle is initiated on the falling edge of WRITE if the Full Flag (

FF) is not set. Data set-

up and hold times must be adhered to with respect to the rising edge of WRITE. Data is stored

in the RAM array sequentially and independently of any ongoing read operation.

SOCP

Serial Output

I

A serial bit read cycle is initiated on the rising edge of SOCP if the Empty Flag (

EF) is not set. In

both Depth and Serial Word Width Expansion modes, all of the SOCP pins are tied together.

NR

Next Read

I

To program the Serial Out data word width , connect

FL/RT

First Load/

I

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

XI grounded),activatingretransmit

(

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

WRITE pointer.

W must be high and SOCP must be low before setting FL/RT LOW. Retransmit

is not compatible with depth expansion. In the depth expansion configuration,

FL/RT grounded

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.

SOX

Serial Output

I

In the Serial Output Expansion mode, the SOX pin of the least significant device is tied HIGH.

clocked out least significant bit first. For single device operation, SOX is tied HIGH.

SO

Serial Output

O

Serial data is output on the Serial Output (SO) pin. Data is clocked out Least Significant Bit first.

In the Serial Width Expansion mode the SO pins are tied together and each SO pin is tristated

at the end of the byte.

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. See the description on page 6 for more details.

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.

Data Set

O

NR to program the Serial Out

word width, etc.

Power Supply

Single Power Supply of 5V.

GND

Ground

Single ground at 0V.

2751 tbl 01