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Architecture
1034
SPRUH82C – April 2013 – Revised September 2016
Copyright © 2013–2016, Texas Instruments Incorporated
Liquid Crystal Display Controller (LCDC)
23.2.3.1.2 Raster Mode
When operating in Raster mode, the DMA engine can generate the interrupts in the following scenarios:
1.
Output FIFO under-run
. This occurs when the DMA engine cannot keep up with the data rate
consumed by the LCD (which is determined by the LCD_PCLK.) This is likely due to a system memory
throughput issue or an incorrect LCD_PCLK setting. The FUF bit in LCD_STAT is set when this error
occurs. This bit is cleared by disabling the Raster Controller (i.e., clearing the LCDEN bit in
RASTER_CTRL).
2.
Frame synchronization lost
. This error happens when the DMA engine attempts to read what it
believes to be the first word of the video buffer but it cannot be recognized as such. This could be
caused by an invalid frame buffer address or an invalid BPP value (for more details, see
). The SYNC bit in the LCD_STAT register is set when such an error is detected. This
field is cleared by disabling the Raster Controller (clearing the LCDEN bit in the RASTER_CTRL
register).
3.
Palette loaded
. This interrupt can be generated when the palette is loaded into the memory by the
DMA engine. At the same time, the PL bit in the LCD_STAT register is set. In data-only (PLM = 2h)
and palette-plus-data (PLM = 00) modes, writing 0 to this bit clears the interrupt. In the palette-only
(PLM = 1) mode, this bit is cleared by disabling the Raster Controller (clearing the LCDEN bit in the
RASTER_CTRL register).
4.
AC bias transition
. If the ACB_I bit in the RASTER_TIMING_2 register is programmed with a non-
zero value, an internal counter will be loaded with this value and starts to decrement each time
LCD_AC_ENB_CS (AC-bias signal) switches its state. When the counter reaches zero, the ABC bit in
the LCD_STAT register is set, which will deliver an interrupt signal to the system interrupt controller (if
the interrupt is enabled.) The counter reloads the value in field ACB_I, but does not start to decrement
until the ABC bit is cleared by writing 0 to this bit.
5.
Frame transfer completed
. When one frame of data is transferred completely, the DONE bit in the
LCD_STAT register is set. This bit is cleared by disabling the Raster Controller (i.e., clearing the
LCDEN bit in the RASTER_CTRL register). Note that the EOF0 and EOF1 bits in the LCD_STAT
register will be set accordingly.
Note that the interrupt enable bits are in the RASTER_CTRL register. The corresponding enable bit must
be set in order to generate an interrupt to the CPU. However, the LCD_STAT register reflects the interrupt
signal regardless of the interrupt enable bits settings.
23.2.3.1.3 Interrupt Handling
See your device-specific data manual for information about the LCD interrupt number to the CPU .The
interrupt service routine needs to determine the interrupt source by examining the LCD_STAT register and
clearing the interrupt properly.
23.2.4 LIDD Controller
The LIDD Controller is designed to support LCD panels with a memory-mapped interface. The types of
displays range from low-end character monochrome LCD panels to high-end TFT smart LCD panels.
LIDD mode (and the use of this logic) is enabled by clearing the MODESEL bit in the LCD control register
(LCD_CTRL).
LIDD Controller operation is summarized as follows:
•
During initialization, the LCD LIDD CS0/CS1 configuration registers (LIDD_CS0_CONF and
LIDD_CS1_CONF) are configured to match the requirements of the LCD panel being used.
•
During normal operation, the CPU writes display data to the LCD data registers (LIDD_CS0_DATA and
LIDD_CS1_DATA). The LIDD interface converts the CPU write into the proper signal transition
sequence for the display, as programmed earlier. Note that the first CPU write should send the
beginning address of the update to the LCD panel and the subsequent writes update data at display
locations starting from the first address and continuing sequentially. Note that DMA may be used
instead of CPU.
•
The LIDD Controller is also capable of reading back status or data from the LCD panel, if the latter has
this capability. This is set up and activated in a similar manner to the write function described above.