2–206

SCF5740/2/4

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 7a. Figure 7b shows that each character

consist of eight 8 bit words. The first word encodes the dis-

play character location and the succeeding seven bytes are

row data. The row data represents the status (On, Off) of indi-

vidual column LEDs. Figure 7c shows that each 8 bit word is

formatted to represent Character Address, or Column Data.

Figure 7d 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 transi-

tion 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 7a, a total of 256 bits of data

are required to load all four characters into the display.

The Character Address Register bits, D4–D0 (Table 2), and

Row Address Register bits, D7–D5 (Table 3), direct the Col-

umn Data bits, D4–D0 (Table 3) to specific RAM location.

Table 7 shows the Row Address for the example character

“D.” Column data is written and read asynchronously from

the 140 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 8 and 9. The character strobe rate is determined by

the internal or user supplied external MUX Clock and the

IC’s

÷ 320 counter.

Table 7. Character “D”

Op code

D7 D6 D5

Column Data

D4 D3 D2 D1 D0

C0 C1 C2 C3 C4

Hex

Row 0 0 0 0

1

1

1

1

0

1E

Row 1 0 0 0

1

0

0

0

1

11

Row 2 0 0 0

1

0

0

0

1

11

Row 3 0 0 0

1

0

0

0

1

11

Row 4 0 0 0

1

0

0

0

1

11

Row 5 0 0 0

1

0

0

0

1

11

Row 6 0 0 0

1

1

1

1

0

1E

Figure 7a–d. Loading Serial Character Data

Character 0

Character 1

Character 2

Character 3

352 Clock Cycles, 70.4 µs

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

Time between LOADS

LOAD

Serial

Clock

DATA

Clock

Period

t 0

D0

D1

D2

D3

D4

D5

D6

D7

11 Clock Cycles, 2.2µs

Time

Between

Loads

600ns(min)

OPCODE

Character Address

OPCODE

Column Data

D7

0

D6

0

D5

0

D4

D

D3

D

Time

Between

Loads

600ns(min)

11 Clock Cycles, 2.2µs

Character 0

Address

Row 0 Column

Data

88 Clock Cycles, 17.6 µs

Row 1 Column

Data

Row 2 Column

Data

Row 3 Column

Data

Row 4 Column

Data

D7

1

D6

0

D5

1

D4

0

D3

0

D2

0

D1

0

D0

0

a.

b.

c.

d.

Row 5 Column

Data

Row 6 Column

Data

D2

D

D1

D

D0

D