PCF8534 datasheet(17/40 Pages) PHILIPS

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PCF8534_0

Preliminary datasheet

Rev. 00.05 — 20 February 2007

17 of 40

NXP Semiconductors

PCF8534

Universal LCD driver for low multiplex rates

6.14 Input bank selector

The input bank selector loads display data into the display RAM in accordance with the

selected LCD drive configuration. Display data can be loaded in bit 2 in static drive mode

or in bits 2 and 3 in 1:2 drive mode by using the BANK SELECT command. The input

bank selector functions independently to the output bank selector.

6.15 Blinker

The display blinking capabilities of the PCF8534 are very versatile. The whole display can

be blinked at frequencies selected by the BLINK command. The blinking frequencies are

integer multiples of the clock frequency. The ratios between the clock and blinking

frequencies depend on the mode in which the device is operating, see Table 7.

An additional feature is for an arbitrary selection of LCD segments to be blinked. This

applies to the static and 1:2 LCD drive modes and is implemented without any

communication overheads. By means of the output bank selector, the displayed RAM

banks are exchanged with alternate RAM banks at the blinking frequency. This mode can

also be specified by the BLINK command.

In the 1:3 and 1:4 multiplex modes, where no alternate RAM bank is available, groups of

LCD segments can be blinked by selectively changing the display RAM data at fixed time

intervals.

If the entire display is to be blinked at a frequency other than the nominal blinking

frequency, this can be effectively performed by resetting and setting the display enable

bit E at the required rate using the MODE SET command.

Table 7.

Blinking frequencies

Blinking mode

Normal operating mode

ratio

Normal blinking frequency

Off

Blinking off

2 Hz

1 Hz

0.5 Hz

CLK

768

-----------

CLK

1536

------------

CLK

3072

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