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UM10503
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User manual
Rev. 1.3 — 6 July 2012
772 of 1269
NXP Semiconductors
UM10503
Chapter 27: LPC43xx LCD
Table 605. Clock and Signal Polarity register (POL, address 0x4000 8008) bit description
Bit
Symbol
Description
Reset
value
4:0
PCD_LO
Lower five bits of panel clock divisor.
The ten-bit PCD field, comprising PCD_HI (bits 31:27 of this
register) and PCD_LO, is used to derive the LCD panel clock
frequency LCDDCLK from the input clock, LCDDCLK =
LCDCLK/(PCD+2).
For monochrome STN displays with a 4 or 8-bit interface, the
panel clock is a factor of four and eight down from the actual
individual pixel clock rate. For color STN displays, 22/3 pixels
are output per LCDDCLK cycle, so the panel clock is 0.375 times
the pixel rate.
For TFT displays, the pixel clock divider can be bypassed by
setting the BCD bit in this register.
Note:
data path latency forces some restrictions on the usable
minimum values for the panel clock divider in STN modes:
Single panel color mode, PCD = 1 (LCDDCLK = LCDCLK/3).
Dual panel color mode, PCD = 4 (LCDDCLK = LCDCLK/6).
Single panel monochrome 4-bit interface mode, PCD =
2(LCDDCLK = LCDCLK/4).
Dual panel monochrome 4-bit interface mode and single panel
monochrome 8-bit interface mode, PCD = 6(LCDDCLK =
LCDCLK/8).
Dual panel monochrome 8-bit interface mode, PCD =
14(LCDDCLK = LCDCLK/16).
0x0
5
CLKSEL
Clock Select.
This bit controls the selection of the source for LCDCLK.
0 = the clock source for the LCD block is CCLK.
1 = the clock source for the LCD block is LCDCLKIN (external
clock input for the LVD).
0x0
10:6
ACB
AC bias pin frequency.
The AC bias pin frequency is only applicable to STN displays.
These require the pixel voltage polarity to periodically reverse to
prevent damage caused by DC charge accumulation. Program
this field with the required value minus one to apply the number
of line clocks between each toggle of the AC bias pin,
LCDENAB. This field has no effect if the LCD is operating in TFT
mode, when the LCDENAB pin is used as a data enable signal.
0x0
11
IVS
Invert vertical synchronization.
The IVS bit inverts the polarity of the LCDFP signal.
0 = LCDFP pin is active HIGH and inactive LOW.
1 = LCDFP pin is active LOW and inactive HIGH.
0x0
12
IHS
Invert horizontal synchronization.
The IHS bit inverts the polarity of the LCDLP signal.
0 = LCDLP pin is active HIGH and inactive LOW.
1 = LCDLP pin is active LOW and inactive HIGH.
0x0