SCF5740 Datasheet, PDF (7/12 Pages) Siemens Semiconductor Group – 0.270” 4-Character, 5x7 Dot Matrix Serial Input Dot Addressable Intelligent Display

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
Row 1 0 0 0
Row 2 0 0 0
Row 3 0 0 0
Row 4 0 0 0
Row 5 0 0 0
Row 6 0 0 0
1 1 1 1 0 1E
1 0 0 0 1 11
1 0 0 0 1 11
1 0 0 0 1 11
1 0 0 0 1 11
1 0 0 0 1 11
1 1 1 1 0 1E
Example: Serial Clock = 5MHz, Clock Period = 200ns
352 Clock Cycles, 70.4 µs
a.
Character 0 Character 1
Character 2
Character 3
88 Clock Cycles, 17.6 µs
b.
Character 0 Row 0 Column Row 1 Column Row 2 Column Row 3 Column Row 4 Column
Address
Data
Data
Data
Data
Data
Row 5 Column
Data
Row 6 Column
Data
11 Clock Cycles, 2.2µs
11 Clock Cycles, 2.2µs
Character Address
OPCODE
Time
Column Data
OPCODE
Time
c.
D7 D6 D5 D4 D3 D2 D1 D0
1 0 1 00 00 0
Between
Loads
600ns(min)
D7 D6 D5 D4 D3 D2 D1 D0
0 0 0 DD D D D
Between
Loads
600ns(min)
LOAD
Serial
Clock
Clock
Period
DATA
d.
D0
D1
D2
D3
D4
D5
D6
D7 Time between LOADS
t0
Figure 7a–d. Loading Serial Character Data
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