W742S81A Datasheet, PDF (34/47 Pages) Winbond – 4 BIT MICROCONTROLLER

W742S81A
Table 7 The relation between the LCDR and segment/common pins used as LCD drive output pins
The LCDON instruction turns the LCD display on (even in HOLD mode), and the LCDOFF instruction
turns the LCD display off. At initial reset, all the LCD segments are unlit. When the initial reset state
ends, the LCD display is turned off automatically. To turn on the LCD display, the instruction LCDON
must be executed.
6.22.1 LCD RAM addressing method
There are 40 LCD RAMs (LCDR00 - LCDR27) that should be indirectly addressed. The LCD RAM
pointer (LP) is used to point to the address of the wanted LCD RAM. The LP is organized as 6-bit binary
register. The MOV LPL,R and MOV LPH,R instructions can load the LCD RAM address to the LP from
R. The MOV @LP,R and MOV R,@LP instructions can access the pointed LCD RAM content.
6.22.2 The output waveforms for the LCD driving mode
1/3 bias 1/4 duty Lighting System (Example)
Normal Operating Mode
COM0
COM1
COM2
COM3
LCD driver
outputs for
only seg. on
COM0 side
being lit
LCD driver
outputs for
only seg. on
COM1 side
being lit
VDD3
VDD2
VDD1
VSS
VDD3
VDD2
VDD1
VSS
VDD3
VDD2
VDD1
VSS
VDD3
VDD2
VDD1
VSS
VDD3
VDD2
VDD1
VSS
VDD3
VDD2
VDD1
VSS
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