NEC PD78F9488 - Manual (Page 263)

CHAPTER 13 LCD CONTROLLER/DRIVER
User’s Manual U15331EJ4V1UD
263
13.7.2 Four-time-slice display example
Figure 13-13 shows how a 14-digit LCD panel having the display pattern shown in Figure 13-12 is connected to the
segment signals (S0 to S27) and the common signals (COM0 to COM3) of the µPD789489 Subseries chip. This
example displays the data "123456.78901234" in the LCD panel. The contents of the display data memory
(addresses FA00H to FA1BH) correspond to this display.
The following description focuses on numeral "6." ( ) displayed as the ninth digit from the right. To display "6." in
the LCD panel, it is necessary to apply the select or deselect voltage to the S16 and S17 pins according to Table 13-6
at the timing of the common signals COM0 to COM3; see Figure 13-12 for the relationship between the segment
signals and LCD segments.
Table 13-6. Select and Deselect Voltages (COM0 to COM3)
Segment S16 S17
Common
COM0 Select Select
COM1 Deselect Select
COM2 Select Select
COM3 Select Select
According to Table 13-7, it is determined that the display data memory location (FA10H) that corresponds to S16
must contain 1101.
Figure 13-14 shows examples of LCD drive waveforms between the S16 signal and the common signals. When
the select voltage is applied to S16 at the timing of COM0, an alternate rectangle waveform, +V
LCD
/-V
LCD
, is generated
to turn on the corresponding LCD segment.
Figure 13-12. Four-Time-Slice LCD Display Pattern and Electrode Connections
Remark n = 0 to 13
;;
;;
;;
;;
;
;
;;
;;
COM0
S 2n
COM1
S
2n+1
COM2
COM3