Each type of liquid crystal display module is now named after its liquid crystal display dots. For example, 12864, it is actually an array of 128 columns and 64 rows. Each model of LCD module will have some of its parameters, let's take a look at some of the principles of 12864.
12864, each display point corresponds to a binary number, 1 means on, 0 means off. The RAM that stores this dot matrix information is called the display data memory. When a certain figure or Chinese character is to be displayed, the corresponding dot matrix information is written into the corresponding storage unit. The dot matrix information of graphics or Chinese characters must of course be designed by yourself. The key to the problem is the situation between the position of the display point on the LCD screen and its address in the memory.
Since most of the LCD module drive circuits are composed of a row driver and two column drivers, the 12864 LCD screen is actually made up of two independent 64*64 LCD screens on the left and right. Each half screen has a 512*8 bits display data RAM. The driving circuit and the memory of the left and right half screens are respectively selected by the chip selection signals CS1 and CS2.
The position of the display point on the 64*64 LCD screen is determined by the line number (line, 0~63)) and the column number (column, 0~63). The address of a memory cell in 512*8 bitsRAM is determined by the page address (Xpage, 0~7) and the column address (Yaddress, 0~63). Each storage unit will store the display information of about 8 liquid crystal dots.
In order to make the corresponding relationship between the position information of the liquid crystal dots and the storage address more intuitive, the 64*64 LCD screen is divided into 8 small display blocks from top to bottom, and each block includes 8 rows * 64 columns of dots. Number of formations. The 8 rows of dot matrix information in each column constitute an 8-bit binary number, which is stored in one of the storage units. It should be noted that the corresponding relationship between the high and low significant bit sequence of the binary system and the line number is different for different businesses.
The RAM area where a display block is stored is called a memory page. That is: the dot matrix information of the 64*64 LCD screen is stored in 8 memory pages, each page has 64 bytes, and each byte stores a column (8 rows) of dot matrix information. Therefore, the memory cell address includes the page address (Xpage, 0~7) and the column address (Yaddress, 0~63).
For example: the liquid crystal dot at the position (20, 30) in the 128*64 screen is lit. Because the column address 30 is less than 64, the dot is in the 29th column of the left half of the screen, so CS1 is valid; OK; Address 20 divided by 8 to get an integer to get 2, and to get the remainder to get 4, the page address of this point in RAM is 2, and the sequence number in the byte is 4; so the binary data is 00010000 (maybe 00001000, high and low order It depends on the manufacturer) write Xpage=2,
In the memory cell with Yaddress=29, the liquid crystal dot on (20, 30) is lit.
