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CHAPTER 17 LCD CONTROLLER/DRIVER
User
’
s Manual U14701EJ3V0UD
17.8.3 4-time-division display example
Figure 17-19 shows the connection of a 4-time-division type 20-digit LCD panel with the display pattern shown
in Figure 17-18 with the
μ
PD780338 Subseries segment signals (S0 to S39) and common signals (COM0 to COM3).
The display example is
“
123456.78901234567890,
”
and the display data memory contents (addresses FA00H to
FA27H) correspond to this.
An explanation is given here taking the example of the 15th digit
“
6.
”
(
in Figure 17-18, selection and non-selection voltages must be output to pins S28 and S29 as shown in Table 17-10
at the COM0 to COM3 common signal timings.
). In accordance with the display pattern
Table 17-10. Selection and Non-Selection Voltages (COM0 to COM3)
Segment
S28
S29
Common
COM0
S
S
COM1
NS
S
COM2
S
S
COM3
S
S
S: Selection, NS: Non-selection
From this, it can be seen that 1101 must be prepared in the display data memory (address FA1CH) corresponding
to S28.
Examples of the LCD drive waveforms between S28 and the COM0 and COM1 signals are shown in Figure 17-
20 (for the sake of simplicity, waveforms for COM2 and COM3 have been omitted). When S28 is at the selection
voltage at the COM0 selection timing, it can be seen that the +V
LCD
/
–
V
LCD
AC square wave, which is the LCD
illumination (ON) level, is generated.
Figure 17-18. 4-Time-Division LCD Display Pattern and Electrode Connections
Remark
n = 0 to 18
COM0
S
2n
COM1
S
2n + 1
COM2
COM3