What is Common Bus System in Computer Architecture?

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A pair of signal lines that facilitate the transfer of multi-bit data from one system to another is known as a bus.

The diagram demonstrates three master devices as M3, M6, and M4.

The master device start and controls the connection. S7, S5, and S2 are slave devices. Slave devices counter to the commands provided by master devices. If M3 needs to offer a command to S5, it should transfer its instruction by the bus.

Therefore, the S5 holds the instruction and takes a response to the instruction by the bus.

A basic computer includes eight registers, a memory unit, and a control unit. These units require to connect frequently. A bus supports the medium through which communication can take place.

There are multiple registers and their functions which are as follows −

  • Load (LD) − During the next clock pulse transition the information from the bus is transmitted to the register whose load (LD) input is enabled.
  • Memory Unit − When the write input of the memory is activated, it holds the content of the bus. When the read input is activated, the memory places the 16-bit output onto the bus with the selection variables being S2S1 S0 = 111..
  • Increment (INR) and Clear (CLR) − When the INR signal is enabled, the contents of the specified register are incremented. The contents are cleared when the CLR signal is enabled.
  • Address Registers (AR) − The address of the memory for the next read and write operation is determined. It receives or sends an address from or to the bus when selection inputs S2S1 S0=001 is used and the load is enabled. With inputs INR and CLR, the address gets incremented or cleared.
  • Program Counter (PC) − The address of the next instruction that is to be read from the memory is saved. It receives or sends an address from or to the bus when selection inputs S2S1 S0 = 010is applied and the load input is enabled. With inputs INR and CLR, the address gets incremented or cleared.
  • Data Register (DR) − The data register includes the data to be written into memory or data that is to be read from the memory. It receives or sends an address from or to the bus when selection inputs are S2S1 S0 = 011 applied and the load input is enabled. With inputs INR and CLR, the address gets incremented or cleared.
  • Accumulator (AC) − Accumulators are beneficial in executing the register micro-operations including complement, shift, etc. The results acquired are again sent to the accumulator. An accumulator stores the intermediate arithmetic and logic results.
  • Instruction Registers (IR) − The IR stores the copy of the instruction that the processor has to implement. The instruction that is read from the memory is stored in the IR. It receives or sends instruction code from or to the bus when selection inputs S2S1 S0 = 111 are applied and the load input is enabled.
  • Temporary Register (TR) − The temporary storage for variables or results is supported by the temporary register. It receives or sends the temporary data from or to the bus when selection inputs S2S1 S0 = 011 are applied and the load input is enabled. With inputs INR and CLR, the address gets incremented or cleared.
  • Input Registers (INPR) − It includes 8 bits to hold the alphanumeric input information. Input device shifts its serial data into the 8-bit register. The data is moved to AC via the adder/logic circuit with load enabled.
  • Output Registers (OUTPR) − The data is received from AC and moved to the output device.
raja
Published on 24-Jul-2021 09:22:29
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