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

Appnote 28

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

3

May 31, 2000-13

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

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

wires. More than 0.2 volt drop (at 100 ma per digit) should be

avoided, since this loss is in addition to any inaccuracies or load

regulation of the power supply.

The 5 volt power supply for the DLO4135/DLG4137 should be

power supply must be used, then local buffers should be used

on all the inputs. These buffers should be powered from the dis-

play power supply. This precaution is to avoid line transients or

Figure 5. Block diagram of the Intel 8031 controller

Interfacing

For an eight digit display using the DLO4135/DLG4137, inter-

facing to a single chip microprocessor such as the 8748, is easy

and straight forward. One approach may be to dedicate one

port for the seven data signals and another 8-bit port for the

write signals. The schematic is shown in Figure 6.

I/O or Memory Mapped System

For a memory mapped system using a processor such as the

8080 or 8085, the interfacing is also straight-forward. Each dis-

play is treated as a memory location with its own address, like

another I/O or RAM location. See Figure 7.

Figure 6. DLO4135/DLG4137 with 8748

8

8

3

8

8

LATCH

BUFFER

EPROM

27xx

DECODER

D Ø

D 7

P3.0

P3.1

P3.2

P3.6

PØ

ALE

8031

A0-A7

OE

PSEN

x

x

x

x

x

8748

6 5 4 3 2 1 0

P2

P1

+

D0

D1

D2

D3

D4

D5

D6

7

6

5

4

3

2

1

0

DLO 4135

DLG 4137

Subroutine to Load an 8-digit Display using the DLO4135/

DLG4137

; DATA IN RAM 10H-17H

(MSD-LSD)

INIT

ORL

P1,#0FFH

; PORT 1 ALL HIGH (WRITE)

ORL

P2,#00H

; PORT 2 ALL LOW (DATA)

MOV

R1,#OFH

; RAM ADDRESS—1

MOV

R2,#0FEH

; WRITE PULSE

MOV

R3,#08H

; COUNTER

START:

INC

R1

; INCREMENT RAM POINTER

DATA:

MOV

A,@R1

; FETCH DATA FROM RAM

OUTL P2,A

; LOAD PORT 2

MOV

A,R2

; RECALL WRITE

RR

A

; SHIFT A TO NEXT WRITE

MOV

R2,A

; SAVE WRITE

WRITE: OUTL P1,A

; SEND WRITE PULSE

MOV

A,#OFFH

; WAIT

OUTL P1,A

; RESET WRITE PULSE

DJNZ

R3,START

; LOAD COMPLETE?

RET

; RETURN TO MAIN PROGRAM

Routine for an 8-Digit Display using the DLO4135/DLG4137

and 8085 or 8080 Microprocessor

; DATA TO BE DISPLAYED IS IN

; A0 (LSD) THRU A7 (MSD)

;

; DISPLAY ADDRESS C00X

; LSD IS RIGHT MOST DIGIT

;

; DOES NOT SAVE REG A,B,H,L,D,E

;

DADD EQU

0A000H

; DATA ADDRESS LOCATION

DPAD

EQU

0C000H

; DISPLAY ADDRESS

LOCATION

LEN

EQU

08H

; DISPLAY LENGTH

;

ORG

100H

;

DISP:

LXI

H,DADD

; LOAD DATA ADDRESS

LXI

D,DPAD

; LOAD DISPLAY ADDRESS

MVI

B,LEN

; LOAD DISPLAY LENGTH

DISP1: MOV

A,M

; GET DATA

XCHG

; XCHG H/L & D/E

MOV

M,A

; LOAD DISPLAY FROM REG A

XCHG

; RESTORE H/L & D/E

INX

D

; INCREMENT DISPLAY ADDRESS

INX

H

; INCREMENT DATA ADDRESS

DCR

B

; DECREMENT LENGTH COUNTER

JNZ

DISP1

; END OF DISPLAY?

RET

; RETURN TO MAIN PROGRAM

8080

or

8085

System

Data

I/OW

Address

Eight DLX413X

A0

A1

A2