COMMERCIALANDINDUSTRIAL

TEMPERATURERANGES

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

4

Symbol

Name

I/O

Description

DataInputs

I

Datainputsforan18-bitbus.

RSA

Reset

I

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

RSB

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

WCLKA

Write Clock

I

When WEN is LOW, data is written into the FIFO on a LOW-to-HIGH transition of WCLK, if the FIFO is not full.

WCLKB

WENA

Write Enable

I

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

WENB

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

RCLKA

Read Clock

I

When REN is LOW, data is read from the FIFO on a LOW-to-HIGH transition of RCLK, if the FIFO is not empty.

RCLKB

RENA

Read Enable

I

When REN is LOW, data is read from the FIFO on every LOW-to-HIGH transition of RCLK. When REN is HIGH,

RENB

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

OEA

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

OEB

state.

LDA

Load

I

When LD is LOW, data on the inputs D0–D11 is written to the offset and depth registers on the LOW-to-HIGH

LDB

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.

FLA

First Load

I

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

FLB

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

synchronous or asynchronous. (See Table I.) 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.

WXIA

Write Expansion

I

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

WXIB

Input

IDT Standard mode or FWFT mode, as well as whether the PAE/PAF flags are synchronous or asynchronous.

(See Table 1.) In the Daisy Chain Depth Expansion configuration, WXI is connected to WXO (Write Expansion

Out) of the previous device.

RXIA

Read Expansion

I

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

RXIB

Input

IDT Standard mode or FWFT mode, as well as whether the PAE/PAF flags are synchronous or asynchronous.

(See Table 1.) In the Daisy Chain Depth Expansion configuration, RXI is connected to RXO (Read Expansion

Out) of the previous device.

FFA/IRA

Full Flag/

O

In the IDT Standard mode, the FF function is selected FF indicates whether or not the FIFO memory is full. In

FFB/IRB

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.

EFA/ORA

Empty Flag/

O

In the IDT Standard mode, the EF function is selected. EF indicates whether or not the FIFO memory is empty.

EFB/ORB

Output Ready

In FWFT mode, the OR function is selected. OR indicates whether or not there is valid data available at the

outputs.

PAEA

Programmable

O

When PAE is LOW, the FIFO is almost-empty based on the offset programmed into the FIFO. The default

PAEB

Almost-Empty flag

offset at reset is 31 from empty for IDT72805LB, 63 from empty for IDT72815LB, and 127 from empty for

IDT72825LB/72845LB.

PAFA

Programmable

O

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

PAFB

Almost-Fullflag

atresetis31fromfullforIDT72805LB,63fromfullforIDT72815LB,and127fromfullforIDT72825LB/72845LB.

WXOA/HFA

WriteExpansion

O

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

WXOB/HFB

Out/Half-FullFlag

depth expansion configuration, a pulse is sent from WXO to WXI of the next device when the last location in

the FIFO is written.

RXOA

Read Expansion

O

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

RXOB

Out

in the FIFO is read.

Data Outputs

O

Data outputs for an 18-bit bus.

Power

+5V power supply pins.

GND

Ground

Ground pins.

PIN DESCRIPTION