PCF85321 NXP [NXP Semiconductors], PCF85321 Datasheet - Page 15

• Manufacturer Part Number: PCF85321
• Description: Universal LCD driver for low multiplex rates
• Manufacturer: NXP [NXP Semiconductors]

NXP Semiconductors
PCF8532_1
Product data sheet
7.11 Data pointer
The addressing mechanism for the display RAM is realized using the 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-MSB and load-data-pointer-LSB commands.
Following this two commands, an arriving data byte is stored starting at the display RAM
address indicated by the data pointer. The filling order is shown in
The data pointer is automatically incremented in accordance with the chosen LCD
configuration.
The contents of the data pointer are incremented as follows:
If the data pointer reaches 159 it is automatically wrapped around to address 0,
consequently the subaddress counter is incremented.
If an I
The data pointer must be re-written prior to further RAM accesses.
Fig 9.
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In 1:3 multiplex mode the bits are placed in row 0, 1 and 2 to three successive
addresses, with bit 2 of the third address left unchanged. 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
row 0, 1, 2 and 3 to two successive display RAM addresses.
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
2
C-bus data access is terminated early then the state of the data pointer is unknown.
backplane outputs
display RAM bits
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.
Display RAM bitmap
(rows)/
(BP)
0
1
2
3
Rev. 1 — 10 February 2009
0
1
2
display RAM addresses (columns)/segment outputs (S)
3
4
Universal LCD driver for low multiplex rates
155 156 157 158 159
Figure
PCF8532
© NXP B.V. 2009. All rights reserved.
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