13. Dot Matrix LCD Controller (H8/3857 Group)
Rev.3.00 Jul. 19, 2007 page 373 of 532
REJ09B0397-0300
13.3.14 Contrast
Control
Circuit
Contrast control can be performed by software (electronic control function) by controlling the
LCD drive voltage (the potential difference between V
LCD
and V1) by means of the contrast control
register (LRA). Variable resistance value V
R
can be adjusted within the range of 0.1 R to 1.6 R,
where R is the value of the basic dividing bleeder resistance between V
LCD
and V1. The contrast
control settings by bits CCR3 to CCR0 in the contrast control register (LRA) are shown in table
13.7.
To ensure stable operation of the voltage follower op-amp circuits that output levels V1 to V5, the
contrast control register (LRA) should be set so that the potential difference between V
LCD
and V1,
and between V5 and V
SS
, is at least 0.4 V. The contrast control ranges are shown in table 13.8.
If contrast control cannot be adequately performed by means of on-chip resistance V
R
, control can
be performed by inserting a resistance between VLOUT and V
LCD
.
Table 13.7 Contrast Control Settings
Contrast Control Register (LRA) Variable Resistance V1
−
V
SS
Potential
CCR3 CCR2 CCR1 CCR0 Value
(V
R
) Difference
Display Color
0 0 0 0 1.6R
Small
Light
1
1.5R
1 0 1.4R
1
1.3R
1 0 0 1.2R
1
1.1R
1 0 1.0R
1
0.9R
1 0 0 0 0.8R
1
0.7R
1 0 0.6R
1
0.5R
1 0 0 0.4R
1
0.3R
1 0 0.2R
1
0.1R
Large
Dark
Summary of Contents for F-ZTAT H8 Series
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