ST6285B View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
'ST6285B' PDF : 78 Pages View PDF
ST62T85B/E85B
4.7 LCD CONTROLLER-DRIVER
On-chip LCD driver includes all features required quartz values. In case of oscillator failure, all seg-
for LCD driving, including multiplexing of the com- ment and common lines are switched to ground to
mon plates. Multiplexing allows to increase display avoid any DC biasing of the LCD elements.
capability without increasing the number of seg-
ment outputs. In that case, the display capability is Table 20. Oscillator Selection Bits
equal to the product of the number of common
plates with the number of segment outputs.
MCU
Oscillator HF2 HF1 HF0
Division Factor
A dedicated LCD RAM is used to store the pattern
to be displayed while control logic generates ac-
cordingly all the waveforms sent onto the segment
or common outputs. Segments voltage supply is
MCU supply independant, and included driving
stages allow direct connection to the LCD panel.
fOSC
0 0 0 Clock disabled: Display off
1.048MHz 0 1 1 32
2.097MHz 1 0 0 64
4.194MHz 1 0 1 128
The multiplexing ratio (Number of common plates)
8.388MHz 1 1 0 256
and the base LCD frame frequency is software Notes:
configurable to achieve the best trade-off con-
trast/display capability for each display panel.
t(s) The 32Khz clock used for the LCD controller is
derivated from the MCU’s internal clock and there-
c fore does not require a dedicated oscillator. The
u division factor is set by the three bits HF0..HF2 of
d the LCD Mode Control Register LCDCR as sum-
ro marized in Table 20 for recommanded oscillator
P Figure 29. LCD Block Diagram
1. The usage fOSC values different from those
defined in this table cause the LCD to operate at a
reference frequency different from 32.768KHz, ac-
cording to division factor of Table 20.
2. It is not recommended to select an internal
frequency lower than 32.768KHz as the clock su-
pervisor circuit may switch off the LCD peripheral
if lower frequency is detected.
lete 1/5 2/5 3/5 4/5
VLCD VLCD VLCD VLCD VLCD
BACKPLANES
SEGMENTS
Obso VOLTAGE
- DIVIDER
COMMON
DRIVER
SEGMENT
DRIVER
lete Product(s) fint
o OSC 32KHz
Obs(When available)
CONTROLLER
32KHz
CLOCK
SELECTION
CONTROL
REGISTER
LCD
RAM
DATA BUS
VR02099A
55/78
55
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