This has to be done with extreme caution as the output of the PLL acts as the main clock signal for the CPU and is also given to other on — chip peripherals that operate on clock signal. If the PLL is miss — configured accidently or deliberately , the microcontroller may not work and the user is responsible. A feed sequence is initialized whenever we are trying to configure PLL. Feed sequence acts as a key to unlock the PLL configuration. For this, we need to know about the other PLL register that we will use.
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Register file This article covers the below mentioned components. Because of the restricted project time, we tend to implement these components in a very behavioral model. Each component is described with an entity. Every entity has its own architecture, which can be optimized for certain necessities depending on its application.
This creates the design easier to construct and maintain. The primary comes from the register file, whereas the other comes from the shifter. Status registers flags modified by the ALU outputs. The V-bit output goes to the V flag as well as the Count goes to the C flag. The ALU has a 4-bit function bus that permits up to 16 opcode to be implemented. Booth Multiplier Factor The multiplier factor has 3 bit inputs and the inputs return from the register file.
The entity representation of the multiplier factor is shown in the above block diagram. This treats positive and negative numbers uniformly. Barrel Shifter The barrel shifter features a bit input to be shifted. This input is coming back from the register file or it might be immediate data. The shifter has different control inputs coming back from the instruction register.
The Shift field within the instruction controls the operation of the barrel shifter. The quantity by which the register ought to be shifted is contained in an immediate field within the instruction or it might be the lower 6 bits of a register within the register file.
The barrel shifter is especially created with multiplexers. Control Unit For any microprocessor, control unit is the heart of the whole process and it is responsible for the system operation,so the control unit design is the most important part within the whole design.
The control unit is sometimes a pure combinational circuit design. Here, the control unit is implemented by easy state machine. The processor timing is additionally included within the control unit. Signals from the control unit are connected to each component within the processor to supervise its operation. The various signals that interface with the processor are input, output or supervisory signals which will be used to control the ARM operation.
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