NXP Semiconductors
PCF8536
Universal LCD low multiplex driver with 6 channel PWM generator
• A clock signal must always be supplied to the device when the display is active.
Removing the clock may freeze the LCD in a DC state, which is not suitable for the
liquid crystal. It is recommended to disable the display first and afterwards to remove
the clock signal.
8.1.4.4 Display enable
The display enable bit (E) is used to enable and disable the display. When the display is
disabled, all LCD outputs go to VSS. This function is implemented to ensure that no
voltage can be induced on the LCD outputs as it may lead to unwanted displays of
segments.
Recommended start-up sequences are found in Section 8.2.3
Remarks:
• The state of display enable has no effect on the GPO outputs.
• Display enable is not synchronized to an LCD frame boundary. Therefore using this
function to flash a display for prolonged periods is not recommended due to the
possible build-up of DC voltages on the display.
8.1.5 Command: oscillator-control
The oscillator-control command switches between internal and external oscillator and
enables or disables the pin OSCCLK. It is also used to define what the external frequency
will be.
Table 10. Oscillator-control - oscillator control command bit description
Bit
Symbol
Value
Description
7 to 3 -
00011
fixed value
2
EFR
external clock frequency applied on pin
OSCCLK
0[1]
9.6 kHz
1
230 kHz
1
COE
clock output enable for pin OSCCLK
0[1]
clock signal not available on pin OSCCLK;
pin OSCCLK is in 3-state
1
clock signal available on pin OSCCLK
0
OSC
oscillator source
0[1]
internal oscillator running
1
external oscillator used;
pin OSCCLK becomes an input;
used in combination with EFR to determine
input frequency
[1] Default value.
The bits OSC, COE, and EFR control the source and frequency of the clock used to
generate the LCD and PWM signals (see Figure 7). Valid combinations are shown in
Table 11.
PCF8536
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 1 — 6 October 2011
© NXP B.V. 2011. All rights reserved.
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