PCF8533USLASH2DASLASH2 datasheet(16/45 Pages) NXP

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PCF8533_4

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Product data sheet

Rev. 04 — 5 March 2010

16 of 45

NXP Semiconductors

PCF8533

Universal LCD driver for low multiplex rates

Once the display RAM of the first PCF8533 has been written, the second PCF8533 is

selected by sending the device-select command again. This time however the command

matches the second device's hardware subaddress. Next the load-data-pointer command

is sent to select the preferred display RAM address of the second PCF8533.

This last step is very important because during writing data to the first PCF8533, the data

pointer of the second PCF8533 is incremented. In addition, the hardware subaddress

should not be changed whilst the device is being accessed on the I2C-bus interface.

7.13 Output bank selector

The output bank selector (see Table 13) 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, these are followed by

the contents of row 1, 2, and then 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

The SYNC signal resets these sequences to the following starting points: bit 3 for

1:4 multiplex, bit 2 for 1:3 multiplex, bit 1 for 1:2 multiplex, and bit 0 for static mode.

The PCF8533 includes a RAM bank switching feature in the static and 1:2 multiplex drive

modes. In the static drive mode, the bank-select command may request the contents of

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

contents of rows 2 and 3 may be selected instead of rows 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. Display data can be loaded in row 2 in static drive mode

or in rows 2 and 3 in 1:2 multiplex drive mode by using the bank-select command. The

input bank selector functions independently to the output bank selector.

7.15 Blinker

The PCF8533 has a very versatile display blinking capability. The whole display can blink

at a frequency selected by the blink-select command. 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, as shown in Table 7.

The entire display can be blinked at a frequency other than the nominal blink frequency by

sequentially resetting and setting the display enable bit E at the required rate using the

mode-set command.

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