PCF8576DTSLASH2 datasheet(20/52 Pages) NXP

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PCF8576D_9

Product data sheet

Rev. 09 — 25 August 2009

20 of 52

NXP Semiconductors

PCF8576D

Universal LCD driver for low multiplex rates

The storage arrangements described lead to extremely efﬁcient data loading in cascaded

applications. When a series of display bytes are sent to the display RAM, automatic

wrap-over to the next PCF8576D occurs when the last RAM address is exceeded.

Subaddressing across device boundaries is successful even if the change to the next

device in the cascade occurs within a transmitted character (such as during the 14th

display data byte transmitted in 1:3 multiplex mode).

The hardware subaddress must not be changed while the device is being accessed on the

I2C-bus interface.

7.13 Output bank selector

The output bank selector selects one of the four bits per display RAM address for transfer

to the display latch. The actual bit chosen depends on the selected LCD drive mode in

operation and on the instant in the multiplex sequence.

• In 1:4 mode, all RAM addresses of bit 0 are selected, these are followed by the

contents of bit 1, bit 2 and then bit 3.

• In 1:3 mode, bits 0, 1 and 2 are selected sequentially

• In 1:2 mode, bits 0 and 1 are selected

• In static mode, bit 0 is selected

The PCF8576D includes a RAM bank switching feature in the static and 1:2 drive modes.

In the static drive mode, the bank-select command (see Section 7.17) may request the

contents of bit 2 to be selected for display instead of the contents of bit 0. In 1:2 mode, the

contents of bits 2 and 3 may be selected instead of bits 0 and 1. This gives the provision

for preparing display information in an alternative bank and to be able to switch to it once it

is assembled.

7.14 Input bank selector

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

selected LCD drive conﬁguration.

The bank-select command (see Section 7.17) can be used to load display data in bit 2 in

static drive mode or in bits 2 and 3 in 1:2 mode. The input bank selector functions are

independent of the output bank selector.

7.15 Blinker

The PCF8576D has a very versatile display blinking capability. The whole display can

blink at a frequency selected by the blink-select command (see Section 7.17). Each blink

frequency is a fraction of the clock frequency; the ratio between the clock frequency and

blink frequency depends on the blink mode selected (see Table 6).

An additional feature allows an arbitrary selection of LCD segments to blink in the static

and 1:2 drive modes. This is implemented without any communication overheads by the

output bank selector which alternates the displayed data between the data in the display

RAM bank and the data in an alternative RAM bank at the blink frequency. This mode can

also be implemented by the blink-select command (see Section 7.17).

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