4-Time-Division Display Example - NEC mPD780344 Series User Manual

18.8.3 4-time-division display example

Figure 18-20 shows the connection of a 4-time-division type 20-digit LCD panel with the display pattern shown
in Figure 18-19 with the 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 from the right "6." ( ). In accordance with the
display pattern in Figure 18-19, selection and non-selection voltages must be output to pins S28 and S29 as shown
in Table 18-9 at the COM0 to COM3 common signal timings.
Table 18-9. Selection and Non-Selection Voltages (COM0 to COM3)
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 common signals are shown in Figure 18-21. When
S28 is at the selection voltage at the COM0 selection timing, it can be seen that the +V
which is the LCD illumination (ON) level, is generated.
Figure 18-19. 4-Time-Division LCD Display Pattern and Electrode Connections
S
S
2n + 1
Remark n = 0 to 18
382
CHAPTER 18 LCD CONTROLLER/DRIVER
Segment
Common
COM0
COM1
COM2
COM3
S: Selection, NS: Non-selection
2n
User's Manual U15798EJ2V0UD
S28 S29
S S
NS S
S S
S S
COM0
COM2
/–V AC square wave,
LCD LCD
COM1
COM3