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PMIC: CP240x LCD Driver Family Slide 16
Now that the different aspects of how liquid crystal displays work have been covered and it is time to do a quick review. This example traces the process to display a complete character. First, the firmware is running and needs to send the number 0 to the first alphanumeric character. The data is written to the ULP memory array that is associated with the segments that form the 0 (the A, B, C, D, E an F segments need to be written to a 1 denoted by the black box). This example is writing to ULPMEM00 which controls the outputs on pins LCD0 and LCD1. Next the LCD controllers outputs are connected to the LCD itself. It can be seen in step three above that the schematic for this board connects LCD0 to pin 35 of the display and LCD1 to pin 1 of the display and the commons are also connected between the controller and the display. COM0 connects to COM0 and so on up through COM3. Each display manufacturer will provide a segment mapping with the pins and the commons. Step four shows how the segments were mapped on this particular display. Knowing that LCD0 connects to pin 36, it can be seen from the listed segments that referencing COM0 drives the decimal point, referencing COM1 drives the C segment, COM2 drives the B segment and COM3 drives the A segment. Similarly, LCD1 connects to the D, E, F and apostrophe segments. Therefore, Writing the value 0x7E to the ULPMEM00 address will set all of the required segments on to display the number 0.
PTM Published on: 2011-05-13