HIEE300024R4 UAA326A04 ABB HIEE300024R4 UAA326A04

UAA326A04

1. The instruction register is used to store the instructions being executed. Instructions are divided into two parts: opcodes and address codes. Opcodes are used to indicate the operation nature of instructions, such as addition, subtraction, etc. The ADDRESS CODE GIVES THE OPERAND ADDRESS OF THIS INSTRUCTION OR INFORMATION ABOUT THE OPERAND ADDRESS FORMATION (IN THIS CASE, THE OPERAND ADDRESS IS FORMED THROUGH THE ADDRESS FORMATION CIRCUIT). There are instructions called transfer instructions, which are used to change the normal order of execution of instructions. The address section of such instructions gives the address of the instruction to be transferred to execution. 2. Opcode decoder: used to decode the opcode of the instruction, generate the corresponding control level, and complete the function of analyzing the instruction. 3, timing circuit: used to generate time marker signal. In a microcomputer, the time flag signal usually has three levels: instruction cycle, bus cycle and clock cycle. Microoperation command generation The circuit generates various microoperation commands that complete the operation specified by the instruction. These commands are generated primarily based on the time flag and the operational nature of the instruction. The circuit is actually the circuit realization of the expression of each microoperation control signal (as above A→L expression), which is the most complex part of the combinatorial 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 execute can be formed by adding 1 to the current address, and 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. This address is in the address field of this transfer instruction, sending it directly to the instruction counter. Microprogram controller is proposed because combinatorial logic design is not easy to design, not flexible, not easy to modify and expand and other shortcomings.

Address instructions are often called single operand instructions. Usually this instruction takes the data in the accumulator register AC as the operand, the number specified in the address field of the instruction word as the operand, and the result of the operation is put back into the accumulator register AC. OP denotes the nature of operation; (AC) represents the number in the accumulation register AC; The address instruction is often called a double operand instruction. Its two address fields indicate the addresses of the two numbers involved in the operation in memory or in the general purpose register of the arithmetic unit