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Control Unit
Published in Pranabananda Chakraborty, Computer Organisation and Architecture, 2020
The design of a digital system, especially a CPU, consists of two typical individual parts: the control unit and the data processing unit. The function of a control unit is to issue control signals to the data processing unit at specified times that selects and sequences the desired data processing operations. Control units can be implemented by way of two distinctive fundamental approaches: hardwired control and microprogrammed control, and both these approaches with their salient features and implementation details have been discussed in the text with their individual strengths and drawbacks. Microinstructions are often interpreted by nanoinstructions which directly control the hardware. The primary objective of the nanoprogramming approach is to save costly CM space, but at the cost of indulging considerably slower execution due to a two-level CM arrangement that is operated in sequence and can never be overlapped. Nanoprogramming is best suited and is found to be most effective when the same microinstructions in CM are found in heavy use.
The 8051 Microcontroller
Published in Zdravko Karakehayov, Knud Smed Christensen, Ole Winther, Embedded Systems Design with 8051 Microcontrollers, 2018
Zdravko Karakehayov, Knud Smed Christensen, Ole Winther
The control unit of a microprocessor or microcontroller is responsible for the proper handling of the stream of instructions. Each instruction includes one or more steps (cycles). At the same time, an instruction can be viewed as a deeper level program which performs a series of specific actions. Executing this program, termed microprogram or microcode, the control unit emerges as a processor within the CPU. There can be no doubt, every processor needs memory to read the instructions. Consequently, the control unit must contain a ROM. Alternatively, the control unit can be designed as a sequential machine. As discussed earlier, CISC computers use microcode. In the case of RISC processors, the control unit can be designed as a FSM. Practically, the users might not be interested in the internal architecture of the microcontroller. However, they should be aware of the timing parameters of the microcomputer and the essential design rules. The topics of this section are the following matters: Basic timing: the interaction between the microcontroller’s CPU and memory.The microcontroller’s instructions parameters: execution time and number of bytes.
Computer Architecture
Published in Bogdan M. Wilamowski, J. David Irwin, Fundamentals of Industrial Electronics, 2018
The control unit of a CPU is responsible for fetching program instructions from memory, interpreting or decoding the instruction codes, and executing instructions by issuing control signals to the elements of the data path. The control unit coordinates all operations of the ALU, memory, and I/O devices by continuously cycling through a set of operations that cause instructions to be fetched from the memory and executed. This sequence of events is called the instruction cycle of the computer, and is illustrated in Figure 23.2. An instruction cycle includes five basic steps: An instruction is fetched from the memory into the control unit of the CPU.The control unit decodes the instruction, i.e., determines from the instruction code what operations to perform.Any data, called operands, needed to perform these operations are accessed from CPU storage registers, retrieved from memory, or read from input devices.The operation is performed on these operands.The result is saved in a register, written to a memory location, or sent to an output device.
Synthesis of programmable biological central processing system
Published in Journal of the Chinese Institute of Engineers, 2021
Wei-Xian Li, Jiangfeng Cheng, Chun-Liang Lin, Chia-Feng Juang
We made use of the Cis-regulatory input function (CRIF) to describe the combined effect of the promoters and logic phenotype. This allowed us to synthesize various Boolean logic gates by selecting the strengths and binding sites of the related DNA bound in the gene’s Cis-regulatory region. We constructed a 4-bit Bio-CPU prototype from several biological logic gates and modules with different functions and a genetic clock source. Structurally, the Bio-CPU consists of three parts, namely a biological arithmetic logic unit (Bio-ALU), a biological control unit (Bio-CU), and a biological memory unit (Bio-MU) (Kuo et al. 2017). The Bio-ALU is responsible for the arithmetic and logic operations, the Bio-CU is responsible for instruction decoding and control command management, and the Bio-MU is responsible for data storage (including instruction storage). Even though several published works have investigated related topics in the synthesis of genetic circuits since the pioneering work unveiled by Hasty, McMillen, and Collins (2002) in Nature, most approaches have implemented combinational genetic circuits without considering the timing-based operation; most works have not implemented the complicated Bio-CPU. The contributions of this paper can thus be summarized as follows: