PCF85133USLASH2DASLASH1 datasheet(14/41 Pages) NXP

14 / 41 page

PCF85133_1

Product data sheet

Rev. 1 — 17 February 2009

14 of 41

NXP Semiconductors

PCF85133

Universal LCD driver for low multiplex rates

• In 1:3 multiplex mode the eight bits are placed in triples into row 0, 1 and 2 of three

successive 4-bit RAM words, with bit 3 of the third address left unchanged. It is not

recommended to use this bit in a display because of the difﬁcult addressing. This last

bit may, if necessary, be controlled by an additional transfer to this address but care

should be taken to avoid overwriting adjacent data because always full bytes are

transmitted.

• In the 1:4 multiplex mode the eight transmitted data bits are placed in quadruples into

row 0, 1, 2 and 3 of two successive 4-bit RAM words.

7.11 Data pointer

The addressing mechanism for the display RAM is realized using a data pointer.

This allows the loading of an individual display data byte, or a series of display data bytes,

into any location of the display RAM. The sequence commences with the initialization of

the data pointer by the load-data-pointer command.

Following this command, an arriving data byte is stored at the display RAM address

indicated by the data pointer. The ﬁlling order is shown in Figure 10.

After each byte is stored, the content of the data pointer is automatically incremented by a

value dependent on the selected LCD drive mode:

• In static drive mode by eight

• In 1:2 multiplex drive mode by four

• In 1:3 multiplex drive mode by three

• In 1:4 multiplex drive mode by two

If an I2C-bus data access is terminated early then the state of the data pointer is unknown.

The data pointer must be re-written prior to further RAM accesses.

The display RAM bitmap shows the direct relationship between the display RAM addresses and

the segment outputs; and between the bits in a RAM word and the backplane outputs.

Fig 9.

Display RAM bitmap

display RAM addresses (columns) / segment outputs (S)

display RAM bits

(rows) /

backplane outputs

(BP)

mgl750

PCF85133U/2DA/1 Datasheet(PDF) 14 Page - NXP Semiconductors