Chapter 1 Hardware Structure
The available division ratios, however, depends on the clock source that is used for the internal
clock source, f
S
. If the clock source for f
S
originates from the WDT oscillator, then only a fixed divi-
sion ratio of f
S
/2
2
is available. If the clock source for f
S
originates from the RTC oscillator, then only
one division ratio of f
S
/2
3
is available. However, if the clock source for f
S
originates from f
SYS
/4, then
a range of LCD clock frequencies are available from f
S
/2
2
to f
S
/2
8
, the value of which is selected by
a further available configuration option. These ratios ensure that for proper LCD operation, a sig-
nal frequency as near as possible to 4kHz, can be selected. For an LCD clock frequency of 4kHz,
the microcontroller LCD driver circuitry will generate an LCD frame frequency between 55Hz and
62Hz. This is in line with the general LCD operating frequency range which lies between 25Hz and
250Hz. Note that if the selected LCD clock frequency is too high, this will result in a higher than re-
quired frame frequency and give rise to higher power consumption while selecting a too low fre-
quency may result in flicker. It is therefore important that if f
SYS
/4 is used as the clock source for f
S
,
the correct configuration option should be chosen to obtain an LCD clock frequency as close to
4kHz as possible.
LCD Driver Output
The number of COM and SEG outputs supplied by the LCD driver, as well as its biasing and duty
options, are dependent upon the device chosen and the configuration options selected. The ac-
companying table lists the various options for each of the devices in the LCD Type MCU series.
Part No.
HT49R30A-1
HT49C30-1
Duty
1/2
1/3
1/4
1/2
HT49R50A-1
HT49C50-1
1/3
1/4
1/2
HT49R70A-1
HT49C70-1
1/3
1/4
1/2
HT49RU80
HT49CU80
1/3
1/4
Driver Number
19´2
19´3
18´4
33´2
33´3
32´4
41´2
41´3
40´4
48´2
48´3
47´4
1/2 or 1/3
C or R type
1/2 or 1/3
C or R type
1/2 or 1/3
C or R type
1/2 or 1/3
C or R type
Bias
Bias Type
LCD Driver Outputs, Duty and Bias Options
Note
The Low Voltage HT49C30L, HT49C50L, HT49C70L devices differ from the other devices in hav-
ing a fixed 1/2 bias and C type bias only, however, they have the same duty and driver number op-
tions as their OTP mask level sister devices.
51
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