7.2 Operation of the GLCD Display

The internal operation of the GLCD display and the KS0108 controller are very complex and beyond the scope of this book. Most microcontroller compiler developers provide libraries for using these displays in their programming languages. mikroC Pro for PIC compiler provides a very advanced GLCD library, and we shall be looking at the details of the functions in this library in the next section. In this section, only the basic information required before using the GLCD library are given.

Figure 7.3 shows the structure of the GLCD, as far as programming the display is concerned. The 128 × 64 pixel display is logically split into two halves. There are two controllers: controller A controlling the left half of the display and controller B controlling the right half, where the two controllers are addressed independently. Each half of the display consists of 8 pages, where each page is 8 bits high and 8 bytes (64 bits) wide. Thus, each half consists of 64 × 64 bits. Text is written to the pages of the display. Thus, a total of 16 characters across can be written for a given page on both halves of the display. Considering that there are 8 pages, a total of 128 characters can be written on the display.

Figure 7.3 Structure of the GLCD

The origin of the display is the top left-hand corner (see Figure 7.4). The X-direction extends towards the right, and the Y-direction extends towards the bottom of the display. In the X-direction, the pixels range from 0 to 127, while in the Y-direction, the pixels range from 0 to 63. Co-ordinate (127, 63) is at the bottom right-hand corner of the display.

Figure 7.4 GLCD display coordinates