LCD controller

According to the principle of TFT-LCD liquid crystal display, the main control signals required for display include pixel clock signals, line/field synchronization signals and enable signals. The function of the LCD controller is to display the drive signal and then drive the LCD. The user only needs to read and write a series of registers to complete the configuration and display drive. In the process of driving LCD design, the most important thing is to configure the LCD controller, and the most important step in configuring the LCD controller is the designation of the frame buffer. The content that the user wants to display is read out from the buffer zone, and then displayed on the screen. The size of the frame buffer is determined by the screen resolution and the number of display colors. The display controller is mainly responsible for obtaining image/video data from the memory or FIFO channel, superimposing and mixing in a certain way, and sending the final image to an external LCD for display, and has a 0, 1, 2 layer FIFO input interface And an external FIFO output interface.

The LCD controller is essentially different from the LCD driver. Simply put, the function of the LCD controller in the embedded system is the same as the function of the graphics card in the computer. The LCD controller is responsible for transmitting the LCD graphic data in the video memory (may be a designated domain in the memory) to the LCD driver , and generates the necessary LCD control signals to control and complete the display, flip, and overlay of the graphics. A series of complex graphics display functions such as zooming. The LCD driver is only responsible for displaying the image data sent by the CPU on the LCD, and will not do any processing on the image.

The LCD controller can be compatible with various CPU interfaces, and the LCD controller can be compatible with various LCD module interfaces. The hardware completes complex image display functions (zoom, flip, overlay, dynamics, etc.) to meet high resolution Display requirements.

According to the speed of the refresh rate, every time you swipe, the display data needs to be read from the memory and output to the LCD display. In this case, the frame rate and the refresh rate should be the same, that is, as long as the content in the memory range pointed to by the LCD controller is changed, the output can be at the speed of the refresh rate. Of course, this memory is very closely related. If the memory speed (bus frequency) cannot keep up, and the refresh rate of the LCD configuration is too fast, it means that the memory bandwidth is not enough, resulting in display flicker or jitter (especially the lower half of the screen). ).