Display Control Unit (DCU)MPC5606S Microcontroller Reference Manual, Rev. 7406 Freescale Semiconductor12.4.3 DCU mode selection and background colorOnce the DCU is configured for use with a particular TFT LCD panel, it can be enabled for use. There arefive modes to choose from, as shown in Table 12-51.The DCU_MODE, PDI_EN and PDI_SLAVE_MODE control bits are in the DCU_MODE register. TheDCU has an interface enable bit for the TFT LCD panel interface called RASTER_EN, also in theDCU_MODE register. When RASTER_EN is 0 the raster scanning of pixels to the panel is disabled butthe pixel clock continues to run as long as DCU_MODE is in an active state.Color bar mode is intended for testing the interface between the DCU and the TFT LCD panel. In thismode, the panel is divided into eight vertical strips of equal width, and the strips display a single colorwhose RGB value is specified in the COLBAR_1 to COLBAR_8 registers. At reset, the colors are set toblack, blue, cyan, green, yellow, red, magenta, and white, where positive logic for the RGB values isassumed. The mode can be used to verify correct connection of the interface to the DCU and correct timingconfiguration of the interface. In this mode, any layer configuration settings are ignored.In Normal mode, the DCU operates according to the timings specified in Section 12.4.2, TFT LCD panelconfiguration, and displays graphics according to the configuration of its layers. The BGND register setsthe RGB color of the background shown when no other layers are present. This background color isincluded in the layer blending process but, since it is always the background, it does not include any layerblending settings.In PDI normal mode, the DCU adopts the timing provided on the PDI interface and replaces thebackground color by the pixel data coming from the PDI interface. The timing values set in the DCU areignored in this mode, and the pixel clock and synchronization signals are taken from the PDI interface andpassed to the TFT LCD panel. The content of the panel is a combination of the incoming pixel stream andlayers generated by the DCU.PDI Slave mode allows the DCU to synchronize with the external timing signals on the PDI input.12.4.4 Proper sequence for enabling and disabling the DCUIt is important to follow a correct sequence when enabling and disabling the DCU.Table 12-51. List of DCU operating modesMode DCU_MODE[1:0] PDI_EN DescriptionOff 00 X DCU disabled; the TFT LCD panel is not driven.Color bar 11 X DCU displays a test pattern consisting of vertical bands of programmablecolor.Normal 01 0 DCU blends layers and displays result on TFT LCD panel.PDI normal 01 1 As normal mode, except that the panel timing is defined by the input onthe PDI interface, and the background color is replaced by the contentprovided on the PDI interface.PDI slave 01 0 The DCU synchronizes its timing to an external signal whenPDI_SLAVE_MODE is enabled.
