PD243X, PD353X, PD443X

2006-01-23

9

There are five registers within the display. Four of these registers

are used to hold the ASCII/attribute code of the four display char-

acters. The fifth register is the Control Word, which is used to blink,

blank, clear, or dim the entire display, or to change the presenta-

tion (attributes) of individual characters.

Adressing

The addresses within the display device are shown below. Digit 0

is the rightmost digit of the display, while digit 3 is on the left.

Although there is only one Control Word, it is duplicated at the four

address locations 0–3. Data can be read from any of these loca-

tions. When one of these locations is written to, all of them will

change together.

Bit D7 of any of the display digit locations is used to allow an at-

tribute to be assigned to that digit. The attributes are discussed in

the next section. If Bit D7 is set to a one, that character will be dis-

played using the attribute. If bit D7 is cleared, the character will dis-

play normally.

Control Word

When address bit A2 is taken low, the Control Word is accessed.

The same Control Word appears in all four of the lower address

spaces of the display. Through the Control Word, the display can

be cleared, the lamps can be tested, display brightness can be

selected, and attributes can be set for any characters which have

been loaded with their most significant bit (D7) set high.

Brightness (D0, D1): The state of the lower two bits of the Control

Word are used to set the brightness of the entire display, from 0%

to 100%. The table below shows the correspondence of these bits

to the brightness.

Attributes (D2–D4): Bits D2, D3, and D4 control the visual

attributes (i.e., blinking) of those display digits which have been

written with bit D7 set high. In order to use any of the four

attributes, the Cursor Enable bit (D4 in the Control Word) must be

set. When the Cursor Enable bit is set, and bit D7 in a character

location is set, the character will take on one of the following dis-

play attributes.

Control Word Format

Address

Contents

A2

A1

A0

0

X

X

Control Word

1

0

0

Digit 0 (rightmost)

1

0

1

Digit 1

1

1

0

Digit 2

1

1

1

Digit 3 (leftmost)

D7

D6

D5

D4

D3

D2

D1

D0

Operation

0

0

X

X

X

X

0

0

Blank

0

0

X

X

X

X

0

1

25% brightness

0

0

X

X

X

X

1

0

50% brightness

0

0

X

X

X

X

1

1

Full brightness

X=don't care

IDCW5163

Enable

Attribute

Blink

Test

Lamp

Clear

Attributes

Brightness

D7

D6

D5

D4

D3

D2

D1

D0

D1 D0 Brightness

0% (blank)

00

25%

01

1

50%

0

1

100%

1

Attributes

Display cursor instead

1

0

0

D3

0

Display blinking cursor

of character

Blink character

0

1

D2

instead of character

1

with cursor

Alternate character

1

Disable above attributes

Attribute Enable

D4

0

Enable above attributes

1

Blink entire display

Blink attribute disabled

Blink

D5

1

0

Standard operation

1

D6

0

Display all dots at 50% brightness

Lamp Test

Clear entire display

Standard operation

0

1

Clear

D7