The principle of 12864 dot matrix LCD module
The 12864 dot matrix liquid crystal display module (LCM) is an array of 128 columns * 64 rows composed of 128 * 64 LCD dots. Each display point corresponds to a binary number, 1 means bright, 0 means off. The RAM that stores these dot matrix information is called display data memory. To display a certain figure or Chinese character is to write the corresponding dot matrix information into the corresponding storage unit. The dot matrix information of graphics or Chinese characters is of course designed by yourself. The key to the problem is the relationship between the position (row and column) of the display dot on the LCD screen and its address in the memory.
Since the drive circuit of most liquid crystal display modules is composed of a row driver and two column drivers, the 12864 LCD screen is actually composed of two independent 64 * 64 LCD screens on the left and right, and each half screen has a 512 * 8 bits show data RAM. The left and right half-screen drive circuits and memory are selected by chip selection signals CS1 and CS2, respectively. (In order to simplify the user design, a few manufacturers add a decoding circuit to the module, so that the 128 * 64 LCD screen is a full screen, and only one chip select signal is required.)
The position of the display point on the 64 * 64 LCD screen is determined by the line number (line, 0 ~ 63) and column number (column, 0 ~ 63). The address of a storage unit in 512 * 8 bits RAM is determined by the page address (Xpage, 0 ~ 7) and the column address (Yaddress, 0 ~ 63). Each storage unit stores the display information of 8 liquid crystal dots.
In order to make the correspondence between the position information of the liquid crystal dots and the storage address more intuitive, the 64 * 64 LCD screen is divided into 8 display blocks from top to bottom, each block includes 8 rows * 64 columns of dot matrix. The 8 rows of dot matrix information in each column constitute an 8-bit binary number, which is stored in a storage unit. (Need to pay attention: the corresponding relationship between the order of binary high and low significant bits and line number is different for different businesses.) The RAM area that stores a display block is called a storage page. That is, the dot matrix information of the 64 * 64 LCD screen is stored in 8 storage pages, each page is 64 bytes, and each byte stores one column (8 rows) of dot matrix information. Therefore, memory cell addresses include page addresses (Xpage, 0 ~ 7) and column addresses (Yaddress, 0 ~ 63).
For example, the liquid crystal dot at the position of (20, 30) in the 128 * 64 screen is lit. Since the column address 30 is less than 64, the dot is in the 29th column of the left half screen, so CS1 is valid; the row address 20 is divided by 8 2. Take the remainder and get 4. The page address in RAM is 2 and the sequence number in the byte is 4; so write binary data 00010000 (may also be 00001000, the order of the high and low depends on the manufacturer) to Xpage = 2 The memory cell with Yaddress = 29 lights up the liquid crystal dots on (20, 30).
The 12864 dot matrix liquid crystal display module (LCM) is an array of 128 columns * 64 rows composed of 128 * 64 LCD dots. Each display point corresponds to a binary number, 1 means bright, 0 means off. The RAM that stores these dot matrix information is called display data memory. To display a certain figure or Chinese character is to write the corresponding dot matrix information into the corresponding storage unit. The dot matrix information of graphics or Chinese characters is of course designed by yourself. The key to the problem is the relationship between the position (row and column) of the display dot on the LCD screen and its address in the memory.
Since the drive circuit of most liquid crystal display modules is composed of a row driver and two column drivers, the 12864 LCD screen is actually composed of two independent 64 * 64 LCD screens on the left and right, and each half screen has a 512 * 8 bits show data RAM. The left and right half-screen drive circuits and memory are selected by chip selection signals CS1 and CS2, respectively. (In order to simplify the user design, a few manufacturers add a decoding circuit to the module, so that the 128 * 64 LCD screen is a full screen, and only one chip select signal is required.)
The position of the display point on the 64 * 64 LCD screen is determined by the line number (line, 0 ~ 63) and column number (column, 0 ~ 63). The address of a storage unit in 512 * 8 bits RAM is determined by the page address (Xpage, 0 ~ 7) and the column address (Yaddress, 0 ~ 63). Each storage unit stores the display information of 8 liquid crystal dots.
In order to make the correspondence between the position information of the liquid crystal dots and the storage address more intuitive, the 64 * 64 LCD screen is divided into 8 display blocks from top to bottom, each block includes 8 rows * 64 columns of dot matrix. The 8 rows of dot matrix information in each column constitute an 8-bit binary number, which is stored in a storage unit. (Need to pay attention: the corresponding relationship between the order of binary high and low significant bits and line number is different for different businesses.) The RAM area that stores a display block is called a storage page. That is, the dot matrix information of the 64 * 64 LCD screen is stored in 8 storage pages, each page is 64 bytes, and each byte stores one column (8 rows) of dot matrix information. Therefore, memory cell addresses include page addresses (Xpage, 0 ~ 7) and column addresses (Yaddress, 0 ~ 63).
For example, the liquid crystal dot at the position of (20, 30) in the 128 * 64 screen is lit. Since the column address 30 is less than 64, the dot is in the 29th column of the left half screen, so CS1 is valid; the row address 20 is divided by 8 2. Take the remainder and get 4. The page address in RAM is 2 and the sequence number in the byte is 4; so write binary data 00010000 (may also be 00001000, the order of the high and low depends on the manufacturer) to Xpage = 2 The memory cell with Yaddress = 29 lights up the liquid crystal dots on (20, 30).
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