366
CHAPTER 12 APPLICATIONS OF LCD CONTROLLER/DRIVER
12.2 4-Time Division Display
This section explains an example using the
μ
PD78064 subseries. Four LCD digits are driven by means of 1/3
bias and 4-time division by using the 16 segment signals (S0 through S15) and four common signals (COM0 through
COM3). Figure 12-12 shows the connection of a 4-time division 4-digit LCD panel with 10 display patterns shown
in Figure 12-11 and the segment (S0 through S15) and common (COM0 through COM4) signals of the
μ
PD78064
subseries. Figure 12-13 shows an example of connecting an LCD drive power supply in the 4-time division display
mode (with external divider resistor, V
DD
= 5 V, and V
LCD
= 5 V). The display example in Figure 12-12 is “12345678”,
and the contents of the display data memory (addresses FA70H through FA7FH) correspond to this.
In this case, “6” at the third digit has been taken as an example. According to the display pattern in Figure 12-
12, the select and unselect voltages shown in Table 12-4 must be output to the S4 and S5 pins in the timing of the
common signals COM0 through COM3.
Table 12-4. Select and Unselect Voltages (COM0, 1, 2, 3)
Segment
S4
S5
Common
COM0
Select (a)
Select (e)
COM1
Unselect (b)
Select (f)
COM2
Select (c)
Select (g)
COM3
Unselect (d)
Select (h)
Remark
(a) through (h) in the table corresponds to the segments a through h in Figure 12-12.
Table 12-4 indicates that 0101 should be stored to the display data memory address (FA7BH) corresponding to
S4.
Figure 12-14 shows the LCD drive waveforms between S4 and COM0 and COM1 signals.
Figure 12-11. Display Pattern of 4-Time Division LCD and Electrode Wiring
Remark
n = 0-7
S2
n
S2
n
+ 1
COM1
COM0
COM2
COM3