HDLO-1414 Просмотр технического описания (PDF) - HP => Agilent Technologies

Номер в каталоге

Компоненты Описание

Список матч

HDLO-1414

Four Character Smart Alphanumeric Displays

HP => Agilent Technologies 

7

Electrical Description

Pin Function

Description

\Write

(\WR, pin 3)

WR must be logic 0 to store data in the

display.

Address Inputs

(A1 and A0, pins

4 and 5)

A0 and A1 select a specific location in the

display memory. Address 00 accesses the far

right character, and address 11 accesses the

far left position.

VDD

(pin 6)

VDD is the positive power supply input.

Ground

(GND, pin 7)

Ground is the display ground.

Data Inputs

(D0–D6, pins 1,

2, 8-12)

D0–D6 are used to specify the input data

for the display.

\WR A1 A0 D6 D5 D4 D3 D2 D1 D0 Function

1 X X X X X X X X X No Change

0 0 0 Digit 0 ASCII Data (Right Most

Character)

0 0 1 Digit 1 ASCII Data

0 1 0 Digit 2 ASCII Data

0 1 1 Digit 3 ASCII Data (Left Most

Character)

Write to

Character

RAM

Figure 1. Display Truth Table

0 = Logic 0; 1 = Logic 1; X = Do Not Care.

Display Internal Block

Diagram

Figure 2 shows the HDLX-1414

display internal block diagram.

The CMOS IC consists of a 4 x 7

Character RAM, a 128-character

ASCII decoder and the refresh

circuitry necessary to

synchronize the decoding and

driving of four 5 x 7 dot matrix

characters.

Four 7-bit ASCII words are stored

in the Character RAM. The IC

reads the ASCII data and decodes

it vita the 128-character ASCII

decoder. This decoder includes

the 64-character set of the HPDL-

1414, 32 lower case ASCII

symbols, and 32 foreign language

symbols.

Data Entry

Figure 1 shows a truth table for

the HDLX-1414 display. Address

inputs A0 and A1 are used to

select the digit location in the

display. When A0 and A1 are both

logic low, data is loaded into the

right most character.

Data inputs D0–D6 are used to

load information into the display.

Data is latched into the given

character address on the rising

edge of the \WR signal. Data and

Address inputs must be held

stable during the write cycle to

ensure that correct data is stored

in the display.

Mechanical and Electrical

Considerations

The HDLX-1414 is a 12-pin DIP

package that can be stacked to

create a character array of any

size. The display is designed to

operate reliably in –40˚C to

+85˚C ambient temperatures.

The HDLX-1414 is assembled by

die attaching and wire bonding

140 LEDs and a CMOS IC to a

high temperature printed circuit

board. A polycarbonate lens is

placed over the PC board,

creating a protective air gap over

the LED wire bonds. Backfill

epoxy environmentally seals the

display package. This package

construction makes the display

highly tolerant to temperature

cycling and allows wave

soldering.

ESD and Latchup

Protection

The inputs to the CMOS IC are

protected against static discharge

and input current latchup.

However, for best results,

standard CMOS handling

precautions should be used. Prior

to use, the HDLX-1414 should be

stored in antistatic tubes or

conductive material. During

assembly a grounded conductive

work area should be used, and

assembly personnel should wear

conductive wrist straps. Lab

coats made of synthetic material

should be avoided since they are

prone to static charge build-up.

Input current latchup can be

caused when the CMOS inputs

are subjected either to a voltage

below ground (Vin < ground) or

higher than VDD (Vin > VDD) and

when a high current is forced into

the input. To prevent input

current latchup and ESD damage,

unused inputs should be

connected either to ground or to

VDD. Voltages should not be

Share Link: