EM6520 EM Microelectronic, EM6520 Datasheet - Page 36

• Manufacturer Part Number: EM6520
• Description: MFP version of EM6620 Ultra Low Power Microcontroller 4x8 LCD Driver
• Manufacturer: EM Microelectronic

12.1 LCD Control
The LCD driver has two control registers
consumption, operation mode and bias voltage source.
LCDExtSupply: Choosing external supply (LcdExtSupply=‘1’) disables the internal LCD voltage regulator and
voltage multiplier, it also puts the bias voltage terminals VL1, VL2 and VL3 into high impedance state. External
bias levels can now be connected to the VL1, VL2 and VL3 terminals. (Resistor divider chain or others).
Another way to adapt the VL1, VL2 and VL3 levels to specific user needs is to overdrive the VL1 output
(LcdExtSupply=0) with the desired value. The internal multiplier will multiply this new VL1 level to generate the
corresponding levels VL2 and VL3. The bit LCDExtSupply is only reset by initial POR.
LCD4Mux: With this switch one selects either 3:1 or 4:1 (default) times multiplexing of the 8 segment driver
outputs. In the case of 3:1 multiplexing the COM[4] is off.
LCDOff: Disables the LCD. The voltage multiplier and regulator are switched off ( 0 current ).The segment
latch information is maintained. The VL1, VL2 and VL3 outputs are pulled to V
LCDBlank: All segment outputs are turned off. The voltage multiplier and regulator remain switched on.
LcdBlank can be used with the 1Hz and Blink interrupt to let the whole display blink (software controlled).
CkTripSel1,0: Selecting the appropriate voltage multiplier frequency to optimize display contrast and power
consumption. The value to use is also depending on the selected multiplier booster capacitors (typically 100nF).
12.2 LCD addressing
The LCD driver addressing is direct using
the registers LCD_0 , LCD_1 , LCD_2 until
LCD_15 . All LCD Segment registers are
R/W..
A total of 16 addresses are available to the
user to define the addressing of the LCD
segment latches. For each of these latches
the user may also choose the data bit to be
connected. See also section 12.3. However
only
implemented. The unused address and bit
locations are empty and can not be used as
RAM.
EM Microelectronic-Marin SA CH-2074 Marin, Switzerland, Tel. [phone], Fax. [phone]
36
8x4
LCD
segment
latches
are
RegLCDCntl1,2
1 6 x 4 d ire c t a d d re s s a b le L C D la tc h e s
L C D _ 1 4
L C D _ 1 3
L C D _ 1 5
L C D _ 1 2
L C D _ 1 1
L C D _ 1 0
L C D _ 9
L C D _ 8
L C D _ 7
L C D _ 6
L C D _ 5
L C D _ 4
L C D _ 2
L C D _ 1
L C D _ 0
L C D _ 3
Figure 26. LCD addressing
b u t m a xim u m 8 x4 b its a r e R /W
to optimize for display contrast,
© EM Microelectonic-Marin SA , 12/98 Rev. A/246
SS
A COMPANY OF
.
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EM6520
power