PCF8545ATT datasheet(13/54 Pages) NXP

13 / 54 page

PCA85276

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Product data sheet

Rev. 3 — 12 November 2018

13 of 54

NXP Semiconductors

PCA85276

Automotive 40 x 4 LCD driver

6.3.4 Writing over the RAM address boundary

In all multiplex drive modes, depending on the setting of the data pointer, it is possible to

fill the RAM over the RAM address boundary. If the PCA85276 is part of a cascade the

additional bits fall into the next device that also generates the acknowledge signal. If the

PCA85276 is a single device or the last device in a cascade, the additional bits are

discarded and no acknowledge signal is generated.

6.3.5 Bank selection

6.3.5.1

Output bank selector

The output bank selector (see Table 9 on page 7) selects one of the four rows per display

RAM address for transfer to the display register. The actual row selected depends on the

particular LCD drive mode in operation and on the instant in the multiplex sequence.

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

contents of row 1, row 2, and then row 3

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

• In 1:2 multiplex mode, rows 0 and 1 are selected

• In static mode, row 0 is selected

6.3.5.2

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 by using the bank-select

command (see Table 9). The input bank selector functions independently to the output

bank selector.

6.3.5.3

RAM bank switching

The PCA85276 includes a RAM bank switching feature in the static and 1:2 multiplex

drive modes. A bank can be thought of as one RAM row or a collection of RAM rows (see

Figure 5). The RAM bank switching gives the provision for preparing display information in

an alternative bank and to be able to switch to it once it is complete.

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