SH79F3283
67
8. Enhanced Function
8.1 LCD Driver
Normal Resistor LCD Driver with Fast charge
The LCD driver contains a controller, a duty cycle generator with 4/8 Common signal pins and 28/27/26/24 Segment driver
pins. Segment 1-28 and COM1-COM4 can also be used as I/O port, it is controlled by the P0SS, P1SS, P2SS, P3SS, register.
LCD COM1-COM8 can be shared with LED Driver. The 28 bytes display data RAM is addressed to 500H-51BH, which could
be used as data memory if needed.
The MCU consists normal display topologies with contrast adjustment which supports both 1/4duty-1/3bias and 1/5duty-1/3
bias, 1/6duty-1/3 bias, 1/6duty-1/4 bias and 1/8duty-1/4 bias driving mode. DISPSEL (DISPCON.7) must be cleared before
LCD working. When ELCC in DISPCON is set, the LCD power supply V
LCD
is selected by VOL[0:3]. When ELCC is cleared,
V
LCD
equals V
DD.
When MCU enters the Power-down mode, the LCD will be turned off. If 32.768kHz crystal/128kHz works in Power-down
mode, the LCD is still working. During the Power in Reset, Pin Reset, LVR Reset and Watchdog Reset, the LCD will be turned
off, and Common and Segment will output low.
The features of the LCD Normal Display Mode include the following:
- LCD clock is decided by code option OP_OSC
- When OP_OSC[3:0] is 1010, 1011 or 1101, LCD clock source is 32.768kHz, DISPCLK0 register is invalid, LCD frame is
64Hz.
- When OP_OSC[3:0] is others, LCD clock source is 128kHz, set DCK[1:0] bits in DISPCLK0 register, select 1/4, 1/3, 1/2, 1/1,
prescaler, so that the
LCD frame is 256/4Hz, 256/3Hz, 256/2Hz, 256/1Hz.
- When OP_OSC[3:0] is 0000, 0001, 1110, in stop mode, the LCD clock will be turned off. When OP_OSC[3:0] is 0011, 0100,
0110, 1010, 1011, 1101, and MCU worked in high frequency mode ,in stop mode, the LCD clock is still working. When
OP_OSC[3:0] is 0011, 0100, 0110, 1010, 1011, 1101, and MCU worked in low frequency mode ,in stop mode, the LCD
clock will be turned off, and the LCD clock is still working in IDLE mode.
- LCD worked 1/4duty-1/3bias and 1/5duty-1/3 bias, 1/6duty-1/3 bias, 1/6duty-1/4 bias and 1/8duty-1/4 bias driving mode by
set DUTY[2:0] bits in DISPCON register.
- 16 levels contrast adjustment by configuring the VOL[3:0] bits in DISPCON register.
- LCD bias resistor (R
LCD
) can be selected as 20K/75K/300K
Ω when select 1/3 bias. LCD bias resistor (R
LCD
) can be selected
as 15K/56K/225K
Ω when select 1/4 bias. The sum LCD bias resistor (R
LCD
) is 60K/225K/900K.
Fast Charge mode or Normal resistor mode is selected by set MOD[1:0] bits in DISPCON1 register. Fast Charge mode can
effectively reduce the power consumption.
When refresh the display data 20k bias resistors are selected to provide larger current to get better LCD display effect, but it
not suitable for some low current consume application. When keep the display data 75K/300k bias resistors are selected to
save drive current, but the LCD display effect will down.
Therefore SH79F3283 provides both the low power consumption and display effect of the display mode. Set MOD[1:0] = 10 to
select this mode. When refresh the display data 20k bias resistors are selected to provide larger current. When keep the
display data 75K/300k bias resistors are selected to save drive current. Charging time is selected as 1/8, 1/16, 1/32 or 1/64 of
LCD com period by FCCTL[1:0] in DISPCON1register.
