 2000 Infineon Technologies Corp. • Optoelectronics Division • San Jose, CA

Appnote 14

www.infineon.com/opto • 1-888-Infineon (1-888-463-4636)

OSRAM Opto Semiconductors GmbH & Co. OHG • Regensburg, Germany

www.osram-os.com • +49-941-202-7178

4

May 31, 2000-12

When using the DLX2416 on a separate display board having

more than 6 inches of cable length, it may be necessary to

buffer all inputs. This is most easily achieved with Hex non-

inverting buffers such as the 74365. The object is to prevent

transient current in the protection diodes. The buffers should

be located on the display board near the displays.

Local power supply bypass capacitors are also needed in many

cases. These should be 6 or 10 volt, tantalum type having 10 µF

or greater capacitance. Low internal resistance is important due

to current steps which result from the internal multiplexing of

the displays.

If small wire cables are used, it is good engineering practice to

calculate the wire resistance of the ground plus the +5 volt

wires. More than 0.1 volt drop, (at 25 mA per digit worst case)

should be avoided, since this loss is in addition to any inaccura-

cies or load regulation limitations of the power supply.

Figure 6. General interface circuit

Figure 7. 16-digit parallel I/O system

Display

Decoder

Display

Display

Display

Vcc

GND

D0–D6

A2

A3

CE

CU

CUE

BL

CLR

WR

A0

A1

D15

D12 D11

D8 D7

D4 D3

D0

0-6

7

Display

Port A

D0

Display

Display

Display

D3

D4

D7

D8

D11

D12

D15

Port B

Port C

0

1

2

3

4

5

6

7

0

1

2

3

4

5

6

7

Control

Data

8080

µP

System

8255

Vcc

GND

D0–D6

CU

CLR

CUE

BL

A0

A1

A2

A3

3

2

1

0

WR

A

B

C

D

7442

5

/

The 5-volt power supply for the displays should be the

play devices. If a separate supply must be used, then local buff-

ers using hex non-inverting gates should be used on all displays

inputs and these buffers should be powered from the display

power supply. This precaution is to avoid logic inputs higher

Program for 16-Character Message

INT:

MVI A,80H

OUT CONTROL

;CONTROL DATA MODE

;LOAD CONTROL REGISTER

CUSR:

MVI A,00H

OUT PORT A

MVI B, 0FH

;CLEAR CURSOR DATA

;LOAD DATA PORT

;SET CHARACTER COUNTER

CUSRI:

MOV A, B

CALL DSPWT

DCR B

JNZ CUSRI

MOV A, B

CALL DSPWT

MVI A, FFH

OUT PORT B

;

;WRITE SUBROUTINE

;DECREMENT COUNTER

;DIGIT 0?

;

;

;SET DATA FOR CONTROL

;LOAD CONTROL LINES

DISP:

LXI H, TABLE

;SET TABLE ADDRESS

DISP1:

MOV A, M

OUT PORT A

MOV A, B

CALL DSPWT

INX H

INR B

MVI A, 10H

CMP B

JNZ DISP1

HALT

;MOVE TABLE DATA INTO

ACCUMULATOR

;LOAD DATA PORT

;

;LOAD ADDRESS AND

CONTROL

;INCREMENT TABLE

ADDRESS

;INCREMENT COUNTER

;SET # OF DIGITS

;

;16 CHARACTERS?

;END OF PROGRAM

DSPWT:

ORI F0H

OUT PORT C

ANI 7FH

OUT PORT C

ORI F0H

OUT PORT C

RET

;SET CONTROL BITS OFF

;LOAD CONTROL

;SET WRITE BIT ON

;LOAD WRITE

;SET WRITE BIT OFF

;LOAD CONTROL

TABLE:

DB

;0C3H

;0C9H

;0D4H

;0D3H

;0C1H

;0D4H

;0CEH

;0C1H

;0C6H

;0A0H

;0D3H

;0D4H

;0C8H

;0C7H

;0C9H

;0CCH