SPBLK01 Control System module

Basic composition of controller:
1. The instruction register is used to store the instructions being executed. The instruction is divided into two parts: the operation code and the address code. The operation code is used to indicate the operation nature of the instruction, such as addition, subtraction, etc. Address code gives the operand address of this instruction or information about forming the operand address (in this case, the address formation circuit is used to form the operand address). There is a kind of instruction called transfer instruction, it is used to change the normal order of execution of instructions, such instruction address code section gives the address of the instruction to be forwarded to execution.
2. Operation code decoder: used to decode the operation code of the instruction, generate the corresponding control level, and complete the function of analyzing the instruction.
3, timing circuit: used to generate time signal. In the microcomputer, the time marker signal generally has three levels: instruction cycle, bus cycle and clock cycle. Microoperation command generation The circuit generates various microoperation commands that complete the operations specified by the instruction. These commands are mainly based on the time stamp and the operational nature of the instruction. The circuit is actually the circuit realization of each microoperation control signal expression (A→L expression above), it is the most complex part of the combinational logic controller.
4. Instruction counter: used to form the address of the next instruction to be executed. Normally, instructions are executed sequentially, and instructions are stored sequentially in memory. So, in general, the address of the next instruction to be executed can be formed by adding 1 to the current address. The microoperation command “1” is used for this purpose. If a transfer instruction is executed, the address of the next instruction to be executed is the address to be transferred to. The address is in the address code field of the transfer instruction and is sent directly to the instruction counter.