PCF8545 datasheet(11/68 Pages) NXP

11 / 68 page

NXP Semiconductors

PCF8545

Universal LCD driver for multiplex rates up to 1:8

7.1.3.4 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 7.2.3

Remark: 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.

7.1.4 Command: oscillator-control

The oscillator-control command switches between internal and external oscillator and

enables or disables the pin OSCCLK. It is also defines the external frequency.

Bit

Symbol

Value

Description

7 to 3

0001 1

fixed value

external clock frequency applied on pin

OSCCLK

0[1]

9.6 kHz

EFR

230 kHz

clock output enable for pin OSCCLK

0[1]

clock signal not available on pin OSCCLK;

pin OSCCLK is in 3-state

COE

clock signal available on pin OSCCLK

oscillator source

0[1]

internal oscillator running

OSC

external oscillator used;

pin OSCCLK becomes an input;

used in combination with EFR to determine

input frequency

Table 9. Oscillator-control - oscillator control command bit description

[1]

Default value.

The bits OSC, COE, and EFR control the source and frequency of the clock used to

generate the LCD signals (see Figure 7). Valid combinations are shown in Table 10.

PCF8545

All information provided in this document is subject to legal disclaimers.

Product data sheet

Rev. 2 — 4 October 2021

11 / 68

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