SCD55100A, SCD55101A, SCD55102A, SCD55103A, SCD55104A
2008-07-22 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 0 0 0 1 1 1 1 0 1E
Row 1 0 0 1 1 0 0 0 1 31
Row 2 0 1 0 1 0 0 0 1 51
Row 3 0 1 1 1 0 0 0 1 71
Row 4 1 0 0 1 1 1 1 0 9E
Charac er 0
Charac er 1
Charac er 2
Charac er 3 Charac er 4
Charac er 5 Charac er 6 Charac er 7 Charac er 8 Charac er 9
660 Clock C cle , 132 μ
Example: Serial Clock = 5 MHz, Clock Period = 200 ns
Time be een LOADS
LOAD
Serial
Clock
DATA
Clock
Period
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
Charac er 0
Addre
Ro 0 Col mn
Da a
66 Clock C cle , 13.2 μ
Ro 1 Col mn
Da a
Ro 2 Col mn
Da a
Ro 3 Col mn
Da a
Ro 4 Col mn
Da a
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.)
