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CHAPTER 18 LCD CONTROLLER/DRIVER
User’s Manual U15798EJ2V0UD
18.6 Common Signals and Segment Signals
An individual pixel on an LCD panel lights when the potential difference of the corresponding common signal and
segment signal reaches or exceeds a given voltage (depending on the panel), and extinguishes when the potential
difference drops lower than V
LCD
.
(1) Common signals
For common signals, the selection timing order is as shown in Table 18-5 according to the number of time divisions
set, and operations are repeated with these as the cycle. In the static mode, the same signal is output to SCOM0.
With a 3-time-division operation, the COM3 pin is left open.
Table 18-5. COM Signals
(2) Segment signals
Segment signals correspond to a 40-byte LCD display RAM (FA00H to FA27H
Note
). Bit 0, bit 1, bit 2, and bit
3 of each display data memory are read in synchronization with the SCOM0/COM0, COM1, COM2 and COM3
timing respectively, and if the value of the bit is 1, it is converted to the selection voltage. If the value of the bit
is 0, it is converted to the non-selection voltage and output to a segment pin (S0 to S39
Note
).
Consequently, it is necessary to check what combination of front surface electrodes (corresponding to the
segment signals) and rear surface electrodes (corresponding to the common signals) of the LCD display to be
used form the display pattern, and then write bit data corresponding on a one-to-one basis with the pattern to
be displayed.
In addition, because LCD display RAM bits 1 to 3 are not used with the static method, these can be used for
other than display purposes.
LCD display RAM bits 4 to 7 are bits for LCD blinking selection. To use the LCD blinking function, set the relevant
bit to 1.
Note
When ports 8 to 11 are used as the segment signal outputs.
COM Signal
Time Division
Static
3-time division
4-time division
Open
COM0
COM1
COM2
COM3
SCOM0
–
–
–
–
–
–
Содержание mPD780344 Series
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