PCF8820U Philips Semiconductors, PCF8820U Datasheet - Page 27

• Manufacturer Part Number: PCF8820U
• Description: 67 x 101 Grey-scale/ECB colour dot matrix LCD driver
• Manufacturer: Philips Semiconductors

Philips Semiconductors
The programming range for the generated V
values above the maximum value of V
user must ensure that the V
the temperature coefficient selected, will never allow the
maximum V
including all tolerances. The customer must also ensure
that the V
V
conditions and including all tolerances.
8.1.8
The PCF8820 has 4 grey-scale registers selected by bits
GR
Each of the 4 registers contain 6 bits allowing to select one
out of the 64 grey levels. A grey-scale register must be
addressed before it can be written to by using the
instruction ‘Grey-scale register’ (see Table 2). The content
of the grey-scale register (bits GS
instruction ‘Grey-scale level control’ (see Table 2). It
should be noted that a grey-scale register setting of 63 is
internally converted to 64. Even numbers are preferred;
odd numbers produce a small DC component in the
waveform of the respective column (see Fig.3).
2000 Dec 07
handbook, full pagewidth
DD1
67 101 Grey-scale/ECB colour dot matrix
LCD driver
(1) Bit PRS = 0: V
(2) Bit PRS = 1: V
0
and GR
or V
V LCD
(V)
G
LCD
DD2
REY
Fig.20 Generated V
LCD
1
, except in the Power-down mode, for all
control register value will never be lower than
00
, which define the four grey intensity levels.
a
-
SCALE REGISTER AND GREY
limit to be exceeded for all conditions and
01
LCD
LCD
b
programming range is LOW.
programming range is HIGH.
02
03
LCD
04
control register value and
LCDOUT
LOW
5
05
to GS
(1)
06
LCD
set by programming V
-
0
. Therefore, the
SCALE LEVEL
. . .
) is set by the
LCDOUT
7D
7E
allows
7F
27
00
The grey-scale level for each pixel is effected by writing the
resultant grey-scale register value into the DDRAM (see
Fig.6).
One of the grey-scale registers can be used to create a
blinking cursor. The intensity of the pixels comprising the
cursor are to be defined by the value in the grey-scale
register. The brightness/colour of the cursor pixels can be
changed by selecting a different grey-scale register
containing a different grey-scale value.
A blinking cursor can be effected by continuously
switching the content of one grey-scale register between
the two grey-scales from e.g. white to black and back
again with a frequency of 2 Hz giving the impression of a
blinking cursor. This procedure causes less load for the
microcontroller than changing all pixels which form the
desired cursor. This implies the display has 3 grey-scale
levels left e.g. off, grey and on.
LCD
01
control register value (bits V
02
03
04
HIGH
05
(2)
06
. . .
7D
OP6
7E
MGT128
Product specification
to V
7F
PCF8820
OP0
register
value
).