PCF85132 Datasheet, PDF (18/54 Pages) NXP Semiconductors – LCD driver for low multiplex rates

NXP Semiconductors
PCF85132
LCD driver for low multiplex rates
columns
display RAM addresses/segment outputs (S)
rows
01234
0
display RAM rows/
backplane outputs ¹
(BP)
2
155 156 157 158 159
3
013aaa220
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 11. Display RAM bitmap
When display data is transmitted to the PCF85132 the received display bytes are stored in
the display RAM in accordance with the selected LCD drive mode. The data is stored as it
arrives and does not wait for the acknowledge cycle as with the commands. Depending on
the current multiplex drive mode, data is stored singularly, in pairs, triples, or quadruples.
To illustrate the filling order, an example of a 7-segment numeric display showing all drive
modes is given in Figure 12; the RAM filling organization depicted applies equally to other
LCD types.
The following applies to Figure 12:
• In static drive mode the eight transmitted data bits are placed in row 0 as one byte.
• In 1:2 multiplex drive mode the eight transmitted data bits are placed in pairs into
row 0 and 1 as two successive 4-bit RAM words.
• In 1:3 multiplex drive mode the eight bits are placed in triples into row 0, 1, and 2 as
three successive 3-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 1:4 multiplex drive mode, the eight transmitted data bits are placed in quadruples
into row 0, 1, 2, and 3 as two successive 4-bit RAM words.
PCF85132
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 1 — 23 November 2010
© NXP B.V. 2010. All rights reserved.
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