4-bit Adder-Subtractor Circuit

The mode input S controls whether the circuit performs addition (S = 0) or subtraction (S = 1).

When S = 1, the circuit complements B and adds 1 through the input carry, effectively calculating A plus the 2's complement of B.

A 4-bit binary incrementer adds one to the binary number in a register, using half-adders to propagate carries through the bits.

<p>Half-adders are used to add the least significant bit to a constant logic-1, enabling the increment operation.</p> Signup and view all the answers

<p>Multiplexers are used to select different arithmetic operations by controlling the data inputs to the adder component.</p> Signup and view all the answers

<p>A circular shift circulates bits around the two ends of the register without data loss, unlike other shifts that may lose information.</p> Signup and view all the answers

<p>The output is generated by the final sum obtained from the cascading half-adders after adding one to the input value.</p> Signup and view all the answers

<p>An arithmetic shift-left multiplies a signed binary number by 2.</p> Signup and view all the answers

<p>Full-adders are crucial for handling carry bits during the addition or subtraction operations, allowing for accurate multi-bit calculations.</p> Signup and view all the answers

<p>An arithmetic shift-right divides the signed binary number by 2.</p> Signup and view all the answers

<p>When performing subtraction, the input carry C0 is set to 1 to account for the addition of 1 while calculating 2's complement.</p> Signup and view all the answers

<p>The sign bit remains unchanged during arithmetic shift operations.</p> Signup and view all the answers

<p>The selection inputs determine the direction of the shift operation, either left or right.</p> Signup and view all the answers

<p>A shifter with n data inputs and outputs requires n multiplexers.</p> Signup and view all the answers

<p>The two serial inputs are used to control the shift left and shift right operations.</p> Signup and view all the answers

<p>The term 'rotate operation' refers to the process of circularly shifting bits around the register, maintaining the data in a continuous loop.</p> Signup and view all the answers

<p>The output of the AND gate for the control function D3D4 becomes active, which clears the sequence counter SC to 0 on the next positive clock transition.</p> Signup and view all the answers

<p>The four phases are: Fetch an instruction from memory, Decode the instruction, Read the effective address from memory if necessary, and Execute the instruction.</p> Signup and view all the answers

<p>The sequence counter SC is incremented after each clock pulse to progress through the timing signals, ensuring the fetch and decode operations occur in sequence.</p> Signup and view all the answers

<p>The instruction is transferred during timing signal T1, where it is read into the instruction register IR while simultaneously incrementing the program counter PC.</p> Signup and view all the answers

<p>It is necessary because only AR is connected to the address inputs of memory, allowing the fetch operation to access the correct instruction.</p> Signup and view all the answers

<p>The AND gate controls when the CLR input of SC is activated, dictating when the counter is cleared and transitioning the circuit based on timing signals.</p> Signup and view all the answers

<p>Decoding the instruction is vital for determining the operation that needs to be executed and understanding any necessary addressing modes.</p> Signup and view all the answers

<p>The instruction cycle stops when a HALT instruction is encountered, terminating the continuous execution of fetch-decode-execute cycles.</p> Signup and view all the answers

<p>The input flag FGI indicates whether new information is available in the input device; it is set to 1 when new information is present and cleared to 0 when the information is accepted by the computer.</p> Signup and view all the answers

<p>When a key is pressed, an 8-bit alphanumeric code is shifted into INPR, and the input flag FGI is set to 1 for the computer to process the input.</p> Signup and view all the answers

<p>The computer checks if the input flag FGI is set to 1; if it is, the information in INPR is transferred to AC, and FGI is cleared to 0.</p> Signup and view all the answers

<p>When the output device is busy, the output flag FGO is cleared to 0, indicating that it cannot accept new information until the current printing is completed.</p> Signup and view all the answers

<p>The 8-bit input register INPR holds alphanumeric input information that is received from the keyboard for processing by the computer.</p> Signup and view all the answers

<p>The output register OUTR receives encoded information from the accumulator (AC) for the output device to print.</p> Signup and view all the answers

<p>Input and output instructions are necessary for transferring information to and from the AC register, checking flag bits, and controlling the interrupt facility.</p> Signup and view all the answers

<p>When FGI is cleared to 0, the computer allows new information to be shifted into INPR by striking another key.</p> Signup and view all the answers

<p>The selection inputs S3S2 determine the type of operation by selecting between arithmetic, logic, and shift operations based on their binary values.</p> Signup and view all the answers

<p>The stored program concept allows computers to store instructions and data in memory, enabling them to execute a sequence of micro operations as defined by programs.</p> Signup and view all the answers

<p>The operation part of an instruction code signifies the specific operation to be performed, such as addition, subtraction, or shifting.</p> Signup and view all the answers

<p>During logic operations, the input carry has no effect and is treated as a don't-care condition (marked with x's).</p> Signup and view all the answers

<p>After reading an instruction from memory, the computer places it in a control register, which interprets the binary code and issues a sequence of micro operations to execute it.</p> Signup and view all the answers

<p>Instruction codes are binary codes that specify a sequence of micro operations for the computer, and they are important because they define what actions the computer will perform.</p> Signup and view all the answers

<p>No, every computer has its own unique instruction set which defines the specific operations it can execute.</p> Signup and view all the answers

<p>Micro operations refer to the fundamental operations that a computer performs on data stored in its registers as specified by the instruction codes.</p> Signup and view all the answers