Philips Semiconductors
Objective specification
Universal LCD driver for small graphic
panels
FEATURES
•
Single-chip LCD controller/driver
•
40 row and 101 column outputs
•
Display data RAM
40
×
101 bits = 505 bytes = 4040 bits
•
On-chip:
– Generation of intermediate LCD bias voltages
– Oscillator requires no external components
(external clock also possible)
•
400 kHz fast I
2
C-bus interface
•
CMOS compatible
•
MUX rate 1 : 40
•
Logic supply voltage range V
DD
−
V
SS
= 2.5 to 6 V
•
Display supply voltage range V
DD
−
V
LCD
= 3.5 to 9 V
•
Low power consumption, suitable for battery operated
systems.
APPLICATIONS
•
Telecom equipment
•
Portable instruments
•
Point of sale terminals
•
Alarm systems.
ORDERING INFORMATION
TYPE
NUMBER
PCF8558U/10
PCF8558U/12
Note
1. For further details see Chapter “Bonding pad locations”.
PACKAGE
(1)
NAME
−
−
chip on FFC
chip with bumps on FFC
DESCRIPTION
GENERAL DESCRIPTION
PCF8558
The PCF8558 is a low power CMOS LCD controller driver,
designed to drive a graphic display of 40 rows and
101 columns. All necessary functions for the display are
provided in a single chip, including on-chip generation of
LCD bias voltages, resulting in a minimum of external
components and lower power consumption.
The PCF8558 interfaces to most microcontrollers via a
I
2
C-bus interface.
VERSION
−
−
1998 Apr 07
2
Philips Semiconductors
Objective specification
Universal LCD driver for small graphic
panels
PINNING
SYMBOL
SCL
R20 to R1
C101 to C1
R21 to R40
T2
SDA
V
SS
T1
V
LCD
SA0
T3
OSC
V
DD
PAD
1
2 to 21
22 to 122
123 to 142
143
144
145
146
147
148
149
150
151
I
2
C-bus serial clock input
LCD row driver data outputs
LCD column driver data outputs
LCD row driver data outputs
test pad output, must be left unconnected (not user accessible)
I
2
C-bus serial data input/output
ground
test pad input, must be connected to V
SS
(not user accessible)
negative supply voltage input
DESCRIPTION
PCF8558
the LSB bit of the I
2
C-bus slave address input is set by connecting this pin to either
0 (V
SS
) or 1 (V
DD
)
test pad input, must be connected to V
DD
(not user accessible)
when the on-chip oscillator is used this pin must be connected to V
DD
; an external clock
signal, if used, is input at this pin
positive supply voltage
1998 Apr 07
4
Philips Semiconductors
Objective specification
Universal LCD driver for small graphic
panels
FUNCTIONAL DESCRIPTION
LCD bias voltage generator
The intermediate bias voltages for the LCD display are
generated and buffered on-chip. This removes the need
for an external resistor bias chain and significantly reduces
the system power consumption.
Oscillator
The on-chip oscillator provides the clock signal for the
display system. No external components are required and
the OSC pin must be connected to V
DD
.
External clock
If an external clock is to be used it is input at the OSC pin.
The resulting display frame frequency is given by
f
OSC
f
frame
=
------------ .
-
3072
Only in the power-down state is the clock allowed to be
stopped (OSC connected to V
SS
), otherwise the LCD will
be frozen in a state where a DC voltage is applied to it.
Power-on reset
The on-chip power-on reset block initializes the chip after
power-on or power failure. This is a synchronous reset and
requires 2 oscillator cycles to execute. These oscillator
cycles must be provided from the external clock source if
the internal oscillator is not used. If this is not done, the
device may not respond to command sequences
transmitted via the I
2
C-bus interface.
Power-down
The chip can be put into power-down mode where all static
currents are switched off (no internal oscillator, no internal
power-on reset, no bias level generation and all LCD
outputs are internally connected to V
DD
) when
PD = logic 1.
During power-down the information in the RAMs and the
internal chip states are preserved. Instruction execution
during power-down is possible if an externally clock signal
is applied to pad OSC.
Registers
The PCF8558 has one 8-bit register, time shared as a
Command Register (CR) and a Data Register (DR).
The command register stores the command code such as
display on or display off and address information for the
Display control
PCF8558
Display Data RAM (DDRAM). Both registers can be written
to but not read from by the system controller.
Address Counter (AC)
The address counter assigns addresses to the DDRAM for
writing and is set by Y2 to Y0 in the command and
X6 to X0 in the address. After a write operation the
address counter is automatically incremented by 1 in
accordance with the V flag.
Display Data RAM (DDRAM)
The PCF8558 contains a 40
×
101-bit static RAM which
stores the display data. The RAM is divided into 5 banks of
101 bytes (5
×
8
×
101 bits). During RAM access, data is
transferred to the RAM via the I
2
C-bus. There is a direct
correspondence between the X address and the column
output number.
Timing generator
The timing generator produces the various signals
required to drive the internal circuitry. Internal chip
operation is not disturbed by operations on the data buses.
The display is generated by continuously shifting rows of
RAM data to the dot matrix LCD via the column outputs.
The display status (all dots on/off and normal/inverse
video) is set by bits E and D in the command word.
LCD row and column drivers
The PCF8558 contains 40 row and 101 column drivers,
which connect the appropriate LCD bias voltages in
sequence to the display in accordance with the data to be
displayed. Figure 3 illustrates typical waveforms. Unused
outputs should be left unconnected.
The bias voltage levels, V2 to V5, are chosen to give
optimum display contrast for a multiplex rate of 1 : 40.
Table 1
Voltage bias levels
VOLTAGE
0.8635
×
(V
DD
−
V
LCD
)
0.7270
×
(V
DD
−
V
LCD
)
0.2730
×
(V
DD
−
V
LCD
)
0.1365
×
(V
DD
−
V
LCD
)
LEVEL
V2
V3
V4
V5
1998 Apr 07
5
RF/Wirelessly
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