W741L250 Datasheet, PDF (23/86 Pages) Winbond – 4-BIT MICROCONTROLLER

W741L250
LCD Controller/Driver
The W741L250 can directly drive an LCD with 24 segment output pins and 4 common output pins for
a total of 24 × 4 dots. Option codes can be used to select one of five options for the LCD driving
mode: static, 1/2 bias 1/2 duty, 1/2 bias 1/3 duty, 1/3 bias 1/3 duty, or 1/3 bias 1/4 duty (see Figure
12). The alternating frequency of the LCD can be set as Fw/64, Fw/128, Fw/256, or Fw/512. In
addition, option codes can also be used to set up four of the LCD driver output pins (segment 0 to
segment 23) as a DC output port. The structure of the LCD alternating frequency (FLCD) is shown in
the figure below.
Timing
Generator
Fosc
Low frequency clock
Divider 0
... ^{Q1 Q2 Q3 Q4 Q5 Q6}
Q14
High frequency clock
Fosc/32
Fw
Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8 Q9
Fw/64
Fw/128
Fw/256
Fw/512
Selector
FLCD
Figure 11. LCD Alternating Frequency (FLCD) Circuit Diagram
LCD Frequency
Selection
Fw
Clock
Generator
DH1
DH2
VDD
VSS
LCD Voltage
Controller
VDD1 to 3
Option Codes
Data Bus
LCD Mode
Controller
LCD Drive
Mode
Selection
FLCD
LCD Duty & Bias
Common
Driver
LCD
Waveform
LCD Data RAM
(24 x 4 bits)
MOV LCDM, #I
Instruction
Segment
Driver/Controller
COM0 to 3
SEG0 to 23
Figure 12. LCD Driver/Controller Circuit Diagram
- 23 -
Publication Release Date: March 1998
Revision A2