3

256 x 18, 512 x 18, 1,024 x 18, 2,048 x 18 and 4,096 x 18

COMMERCIALANDINDUSTRIAL

TEMPERATURERANGES

MARCH 2013

PIN DESCRIPTION

Symbol

Name

I/O

Description

D0–D17

DataInputs

I

Data inputs for an 18-bit bus.

RS

Reset

I

WhenRS issetLOW,internalreadandwritepointersaresettothefirstlocationoftheRAMarray,FFand PAF

go HIGH, and PAE and EF go LOW. A reset is required before an initial WRITE after power-up.

WCLK

WriteClock

I

WhenWENisLOW,dataiswrittenintotheFIFOonaLOW-to-HIGHtransitionofWCLK,iftheFIFOisnotfull.

WEN

WriteEnable

I

When WEN is LOW, data is written into the FIFO on every LOW-to-HIGH transition of WCLK. When WEN is

HIGH, the FIFO holds the previous data. Data will not be written into the FIFO if the FF is LOW.

RCLK

Read Clock

I

WhenRENisLOW,dataisreadfromtheFIFOonaLOW-to-HIGHtransitionofRCLK,iftheFIFOisnotempty.

REN

Read Enable

I

WhenRENisLOW,dataisreadfromtheFIFOoneveryLOW-to-HIGHtransitionofRCLK. WhenRENisHIGH,

the output register holds the previous data. Data will not be read from the FIFO if the EF is LOW.

OE

OutputEnable

I

WhenOEisLOW,thedataoutputbusisactive.IfOE isHIGH,theoutputdatabuswillbeinahigh-impedance

state.

LD

Load

I

When LDisLOW,dataontheinputsD0–D11iswrittentotheoffsetanddepthregistersontheLOW-to-HIGH

transition of the WCLK, when WEN is LOW. When LD is LOW, data on the outputs Q0–Q11 is read from the

offset and depth registers on the LOW-to-HIGH transition of the RCLK, when REN is LOW.

FL

FirstLoad

I

In the single device or width expansion configuration, FL together with WXI and RXI determine if the mode is

IDT Standard mode or First Word Fall Through (FWFT) mode, as well as whether the PAE/PAF flags are

synchronous or asynchronous. (See Table 1.) In the Daisy Chain Depth Expansion configuration, FL is

grounded on the first device (first load device) and set to HIGH for all other devices in the Daisy Chain.

WXI

WriteExpansion

I

In the single device or width expansion configuration, WXI together with FL and RXI determine if the mode

Input

isIDTStandardmodeorFWFTmode,aswellas whetherthePAE/PAFflagsaresynchronousorasynchronous.

(SeeTable1.) IntheDaisyChainDepthExpansionconfiguration,WXIisconnectedtoWXO(WriteExpansion

Out) of the previous device.

RXI

Read Expansion

I

In the single device or width expansion configuration, RXI together with FL and WXI, determine if the mode

Input

isIDTStandardmodeorFWFTmode,aswellas whetherthePAE/PAFflagsaresynchronousorasynchronous.

(SeeTable1.) IntheDaisyChainDepthExpansionconfiguration,RXIisconnectedtoRXO(ReadExpansion

Out) of the previous device.

FF/IR

Full Flag/

O

IntheIDTStandardmode,the FFfunctionisselected. FF indicateswhetherornottheFIFOmemoryisfull.In

Input Ready

the FWFT mode, the IR function is selected. IR indicates whether or not there is space available for writing to

the FIFO memory.

EF/OR

EmptyFlag/

O

IntheIDTStandardmode,theEFfunctionisselected.EFindicateswhetherornottheFIFOmemoryisempty.

OutputReady

InFWFTmode,theORfunctionisselected.ORindicateswhetherornotthereisvaliddataavailableattheoutputs.

PAE

Programmable

O

WhenPAEisLOW,theFIFOisalmost-emptybasedontheoffsetprogrammedintotheFIFO.Thedefault

Almost-EmptyFlag

offsetatresetis31fromemptyforIDT72V205,63fromemptyforIDT72V215,and127fromemptyforIDT72V225/

72V235/72V245.

PAF

Programmable

O

WhenPAFisLOW,theFIFOisalmost-fullbasedontheoffsetprogrammedintotheFIFO.Thedefaultoffsetat

Almost-FullFlag

resetis31fromfullforIDT72V205,63fromfullforIDT72V215,and127fromfullforIDT72V225/72V235/72V245.

WXO/HF

WriteExpansion

O

In the single device or width expansion configuration, the device is more than half full when HF is LOW. In the

Out/Half-FullFlag

depthexpansionconfiguration,apulseissentfromWXOtoWXIofthenextdevicewhenthelastlocationinthe

FIFOiswritten.

RXO

Read Expansion

O

In the depth expansion configuration, a pulse is sent from RXO to RXI of the next device when the last

Out

location in the FIFO is read.

Q0–Q17

DataOutputs

O

Data outputs for an 18-bit bus.

Power

+3.3V power supply pins.

GND

Ground

Seven ground pins.