ST62T45B STMicroelectronics, ST62T45B Datasheet - Page 48
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ST62T45B
Manufacturer Part Number
ST62T45B
Description
8-BIT OTP/EPROM MCU
Manufacturer
STMicroelectronics
Datasheet
1.ST62T45B.pdf
(72 pages)
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ST62T45B/E45B
4.5 LCD CONTROLLER-DRIVER
On-chip LCD driver includes all features required
for LCD driving, including multiplexing of the com-
mon plates. Multiplexing allows to increase dis-
play capability without increasing the number of
segment outputs. In that case, the display capabil-
ity is equal to the product of the number of com-
mon plates with the number of segment outputs.
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.
The multiplexing ratio (Number of common plates)
and the base LCD frame frequency is software
configurable to achieve the best trade-off con-
trast/display capability for each display panel.
The 32Khz clock used for the LCD controller is
derivated from the MCU’s internal clock and there-
fore does not require a dedicated oscillator. The
division factor is set by the three bits HF0..HF2 of
the LCD Mode Control Register LCDCR as sum-
marized in Table 17 for recommanded oscillator
Figure 26. LCD Block Diagram
48/72
(When available)
OSC 32kHz
f
int
VLCD
VOLTAGE
DIVIDE R
VLCD VLCD
1/3
SELECTION
CLOCK
2/3
32kHz
CONTROLLER
BACKPLAN ES
COMMON
DRIVE R
quartz values. In case of oscillator failure, all seg-
ment and common lines are switched to ground to
avoid any DC biasing of the LCD elements.
Table 17. Oscillator Selection Bits
Notes:
1.
defined in this table cause the LCD to operate at a
reference frequency different from 32.768kHz, ac-
cording to division factor of Table 17.
2.
frequency lower than 32.768kHz as the clock su-
pervisor circuit may switch off the LCD peripheral
if lower frequency is detected.
Oscillator
1.048MHz
2.097MHz
4.194MHz
8.388MHz
MCU
f
OSC
The usage f
It is not recommended to select an internal
REGISTER
CONTROL
HF2 HF1 HF0
0
0
1
1
1
DATA BUS
OSC
0
1
0
0
1
SEGMENT
SEGMENTS
DRIVER
values different from those
0
1
0
1
0
Clock disabled: Display off
32
64
128
256
Division Factor
RAM
LCD
VR02099