SCD55100A, SCD55101A, SCD55102A, SCD55103A, SCD55104A

2006-02-20

8

The following explains how to format the serial data to be loaded

into the display. The user supplies a string of bit mapped decoded

characters. The contents of this string is shown in Figure „Loading

Serial Character Data a“ (page 8). Figure „Loading Serial Charac-

ter Data b“ (page 8) shows that each character consist of six 8 bit

words. The first word encodes the display character location and

the succeeding five bytes are row data. The row data represents

the status (On, Off) of individual column LEDs. Figure „Loading

Serial Character Data c“ (page 8) shows that each 8 bit word is

formatted to include a three bit Operational Code (OPCODE)

defined by bits D7–D5 and five bits (D4–D0) representing Column

Data, Character Address, or Control Word Data.

Figure „Loading Serial Character Data d“ (page 8) shows the

sequence for loading the bytes of data. Bringing the LOAD line low

enables the serial register to accept data. The shift action occurs

on the low to high transition of the serial data clock (SDCLK). The

least significant bit (D0) is loaded first. After eight clock pulses the

LOAD line is brought high. With this transition the OPCODE is

decoded. The decoded OPCODE directs D4–D0 to be latched in

the Character Address register, stored in the RAM as Column

data, or latched in the Control Word register. The control IC

requires a minimum 600 ns delay between successive byte loads.

As indicated in Figure „Loading Serial Character Data a“ (page 8),

a total of 660 clock cycles (60-8 bit words) are required to load all

ten characters into the display.

The Character Address Register bits, D4–D0 (Table „Load Charac-

ter Address“ (page 9)) and Row Address Register bits, D7–D5

(Table „Load Column Data“ (page 9)) direct the Column Data bits,

D4–D0 (Table „Load Column Data“ (page 9)) to specific RAM loca-

tion. Table „Character ’D’“ (page 8) shows the Row Address for the

example character “D.” Column data is written and read asynchro-

nously from the 250 bit RAM. Once loaded the internal oscillator

and character multiplexer reads the data from the RAM. These

characters are row strobed with column data as shown in Figures

„Row and Column Location“ (page 9) and „Row Strobing“

(page 10). The character strobe rate is determined by the internal

or user supplied external MUX Clock and the IC’s ÷ 320 counter.

Loading Serial Character Data

Character “D”

Op code

D7

D6 D5

Column Data

D4

D3

D2

D1

D0

C0

C1

C2

C3

C4

Hex

Row 0

00

0

11

1

1

0

1E

Row 1

00

1

10

0

0

1

31

Row 2

01

0

10

0

0

1

51

Row 3

01

1

10

0

0

1

71

Row 4

10

0

11

1

1

0

9E

Character 0

Character 1

Character 2

Character 3

Character 4

Character 5

Character 6

Character 7

Character 8

Character 9

660 Clock Cycles, 132

µs

Example: Serial Clock = 5 MHz, Clock Period = 200 ns

Time between LOADS

LOAD

Serial

Clock

DATA

Clock

Period

t

0

D0

D1

D2

D3

D4

D5

D6

D7

11 Clock Cycles, 2.2 s

Time

Between

Loads

OPCODE

Character Address

OPCODE

Column Data

D0

C4

D1

C3

D2

C2

D3

C1

D4

C0

Character 0

Address

Row 0 Column

Data

66 Clock Cycles, 13.2

µs

Row 1 Column

Data

Row 2 Column

Data

Row 3 Column

Data

Row 4 Column

Data

D0

0

D1

0

D2

0

D3

0

D4

0

D5

1

D6

0

D7

0

D5 D6 D7

a.

b.

c.

d.

11 Clock Cycles, 2.2 s

600 ns(min.)

Time

Between

Loads

600 ns(min.)