PCF8576C Philips Semiconductors, PCF8576C Datasheet - Page 16

• Manufacturer Part Number: PCF8576C
• Description: Universal LCD driver for low multiplex rates
• Manufacturer: Philips Semiconductors

Philips Semiconductors
6.11
The display RAM is a static 40
LCD data. A logic 1 in the RAM bit-map indicates the on
state of the corresponding LCD segment; similarly, a
logic 0 indicates the off state. There is a one-to-one
correspondence between the RAM addresses and the
segment outputs, and between the individual bits of a RAM
word and the backplane outputs. The first RAM column
corresponds to the 40 segments operated with respect to
backplane BP0 (see Fig.10). In multiplexed LCD
applications the segment data of the second, third and
fourth column of the display RAM are time-multiplexed
with BP1, BP2 and BP3 respectively.
When display data is transmitted to the PCF8576C the
display bytes received are stored in the display RAM in
accordance with the selected LCD drive mode.
To illustrate the filling order, an example of a 7-segment
numeric display showing all drive modes is given in Fig.11;
the RAM filling organization depicted applies equally to
other LCD types.
With reference to Fig.11, in the static drive mode the eight
transmitted data bits are placed in bit 0 of eight successive
display RAM addresses.
1998 Jul 30
Universal LCD driver for low multiplex
rates
Display RAM
Fig.10 Display RAM bit-map showing direct relationship between display RAM addresses
backplane outputs
display RAM bits
(columns) /
and segment outputs, and between bits in a RAM word and backplane outputs.
(BP)
4-bit RAM which stores
0
1
2
3
0
1
2
display RAM addresses (rows) / segment outputs (S)
3
4
16
In the 1 : 2 multiplex drive mode the eight transmitted data
bits are placed in bits 0 and 1 of four successive display
RAM addresses. In the 1 : 3 multiplex drive mode these
bits are placed in bits 0, 1 and 2 of three successive
addresses, with bit 2 of the third address left unchanged.
This last bit may, if necessary, be controlled by an
additional transfer to this address but care should be taken
to avoid overriding adjacent data because full bytes are
always transmitted. In the 1 : 4 multiplex drive mode the
eight transmitted data bits are placed in bits 0, 1, 2 and 3
of two successive display RAM addresses.
Table 3 LCD frame frequencies
Normal mode
Power-saving mode
PCF8576C MODE
35
36
FREQUENCY
37
FRAME
------------ -
2880
--------- -
480
f
f
clk
clk
38
MBE525
39
Product specification
PCF8576C
FREQUENCY
NOMINAL
FRAME
(Hz)
64
64