Research And Design Of A 8 Bit Microcontroller Compatible With MCS-51 Instruction Set

The microcontroller (MCU) which is always an extreme challenging design in the Integrated Circuit (IC) plays an important part in the digital system design. With its powerful function and strong field programming, it is widely used in the digital system design such as the industrial control and the system on chip (SOC) design and so on.Based on XI'DIAN university's scientific research project: Theoretical research on the key technique and the design for deep-submicron mixed signal ASIC, an 8 bit microcontroller(MCU) which belongs to the CSIC microcontroller and can be compatible with the MCS-51 instruction set was designed. This MCU is designed by HARVARD structure in which the data bus and the instruction bus are divided so that the control structure can be simplified and the data processing can be accelerated .The design of the data bus in the MCU implied the method of driving on different segment by different sources which can avoid generating the three state circuits so that the backend design becomes easy. The method of taking the clock signal as the flip-flop's enable is used into the design of the counter (TIMER) and the serial communication (UART) modules so that the whole MCU will work on the same clock which is useful for the RTL synthesizing and the backend tool's processing.Firstly, the MCS-51 series of MCU's systematic structure, the instruction set and the timing of the instruction's execution were deeply analyzed in this paper, secondly ,the top to down analytical method was introduced to analyze the MCU and at the same time each modules functional specification were given. Then, with the designing method of down to top, the sub-modules were realized with Verilog language and gradually the whole MCU. Lastly, the designed MCU was simulated by the software of ModelSim. The simulation results showed that the designed MCU can execute all the instructions correctly and can be perfectly compatible with MCS-51 series of the MCU. The subsidiary function modules which contain timer, interruption system as well as UART performed well and fitted the demands of our design.