ST7781
8. System Interface
8.1 Interface Specifications
ST7781 has the system interface to read/write the control registers and display memory (DRAM) displaying a moving
picture. User can select an optimum interface to display the moving or still picture with efficient data transfer. All display
data are stored in the DRAM to reduce the data transfer efforts and only the updating data is necessary to be transferred.
User can only update a sub-range of DRAM by using the window address function.
ST7781 adopts 18-bit bus interface architecture for high-performance microprocessor. All the functional blocks of ST7781
starts to work after receiving the correct instruction from the external microprocessor by the 18bits, 16bits, 9bits,8bits. The
index register (IR) stores the register address to which the instructions and display data will be written. The data/command
selection signal (RS), the read/write signals (/RD//WR) and data bus DB[17:0] are used to read/write the instructions and
data of ST7781. The registers of the ST7781 are categorized into the following groups.
1. Specify the Index of Register (IR)
2. Read a Status
3. Display Control
4. Power Management Control
5. Display Data Processing
6. Set Internal DRAM Address (AC)
7. Transfer Data to/from the Internal DRAM (R22h)
8. Internal Grayscale γ-Correction (R30h ~ R3Dh)
Normally, the display data (DRAM) is most often updated, and in order since the ST7781 can update internal DRAM
address automatically as it writes data to the internal DRAM and minimize data transfer by using the window address
function, there are fewer loads on the program in the microprocessor.
Ver. 1.7
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