W742C813 Datasheet, PDF (41/56 Pages) Winbond – 4 BIT MICROCONTROLLER

W742E/C813
5.25 LCD Controller/Driver
The W742E/C813 can directly drive an LCD with 40 segment output pins and 16 common output pins
for a total of 40 × 16 dots. The LCD driving mode is 1/5 bias 1/8 or 1/16 duty. The alternating frequency
of the LCD can be set as Fw/16, Fw/32, Fw/64, or Fw/128. The structure of the LCD alternating
frequency (FLCD) is shown in the Figure 5-17.
Fw
Sub-oscillator clock
Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8 Q9
Fw/16
Fw/32
Fw/64
Fw/128
Selector
FLCD
Figure 5-17 LCD alternating frequency (FLCD) circuit diagram
Fw = 32.768 KHz, the LCD frequency is as shown in the table below.
Table 5 The relartionship between the FLCD and the duty cycle
LCD Frequency
Fw/128 (256 Hz)
Fw/64 (512 Hz)
Fw/32 (1024 Hz)
Fw/16 (2048 Hz)
1/8 Duty
32
64
128
-
1/16 Duty
-
32
64
128
Corresponding to the 40 LCD drive output pins, there are 160 LCD data RAM segments. Instructions
such as MOV LPL,R, MOV LPH,R, MOV @LP,R, and MOV R,@LP are used to control the LCD data
RAM. The data in the LCD data RAM are transferred to the segment output pins automatically without
program control. When the bit value of the LCD data RAM is "1," the LCD is turned on. When the bit
value of the LCD data RAM is "0," LCD is turned off. The contents of the LCD data RAM (LCDR) are
sent out through the segment0 to segment39 pins by a direct memory access. The relation between
the LCD data RAM and segment/common pins is shown below.
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Publication Release Date: December 2000
Revision A1