# 4-bit 8-instruction Alu

6502.org Tutorials and Aids. I am making 4 bit ALU here i have declared entities entity ALU is Port ( a : in STD_LOGIC_VECTOR (3 downto 0);); end ALU; can you please explain that how, The arithmetic and logic unit has 4-bit select inputs to select one from 16 operations as shown in Table.1. Two 8-bit data are given as input to the ALU. The logical operations include all basic logic gates. The various sub modules in the design are adder/subtractor, multiplier and a logical unit. Table 1 : Operations in the ALU . I3 . I2 . I1 . I0 . Operation.

### Lecture2 TheCPUInstructionFetch&Execute

Register file Wikipedia. I am making 4 bit ALU here i have declared entities entity ALU is Port ( a : in STD_LOGIC_VECTOR (3 downto 0);); end ALU; can you please explain that how, VHDL ALU, alu vhdl, vhdl code for alu, alu in vhdl, alu vhdl project.

The instruction set and architecture of the 8-bit microcontroller are available at Chapter 13 in the book "Introduction to Logic an Arithmetic Logic Unit 2012-12-07В В· More information here: http://letsbuild.me/letsbuild/8_bit_c... The ALU is one of the central building blocks of every computer. Follow me on twitter

VHDL for FPGA Design/4-Bit ALU. From Wikibooks, open books for an open world < VHDL for FPGA Design. This page may need to be reviewed for quality. 2014-11-16В В· Instruction is 4 bit 16 instructions Data is 8 bit ALU is 8 bit Program memory is 4x16 bit Data memory is 8 x 256 bit 4 to 16 Instruction decoder Program counter 4 bit Q1.Why ALU is 8 bit ? Because the data is 8 bit so ALU should be 8 bit Q2.Why Program memory is 4x16 bit ? Instruction are 4 bits so program mmory should be 4x16 bit

8-Bit Arithmetic Logic Unit it is the heart of the instruction execution portion of every computer. ECE 547 - UNIVERSITY OF MAINE 4 Fig. 2. 8 Bit ALU 2012-05-03В В· How to Build an 8-Bit of this Instructable will be a computer that you can program with a unique instruction set. (arithmetic logic unit)

CS 150 - Spring 2001 - Computer Organization - 8 Instruction Types z Data y 4-bit, 8-bit, 16-bit PC ALUout load esultr of ncriementing ni ALU into PC Muduli, Giridhari, et al. "Design of an Efficient Low Power 4-bit Arithmatic Logic Unit (ALU) Using VHDL." International Transaction of Electrical and Computer

Lab 8:16 Bit Arithmetic/Logic Unit Design Objective: Design, synthesize, and simulate a 16 bit ALU with specified operation. 16-bit ALU Specification: 1998 Jun 10 2 Philips Semiconductors Product speciп¬Ѓcation 4-bit arithmetic logic unit 74HC/HCT181 FEATURES вЂўFull carry look-ahead for high-speed arithmetic

The Z-80 has a 4-bit ALU. In this circuit, simple logic gates select one of eight bits based on the instruction. The 8-bit result is written to the ALU bus, 1998 Jun 10 2 Philips Semiconductors Product speciп¬Ѓcation 4-bit arithmetic logic unit 74HC/HCT181 FEATURES вЂўFull carry look-ahead for high-speed arithmetic

Computer Architecture ECE 361 Lecture 5: By the end of Branch instruction, В° 1-bit ALU 4-bit ALU A B 1-bit Full Adder CarryOut Mux 2012-05-03В В· How to Build an 8-Bit of this Instructable will be a computer that you can program with a unique instruction set. (arithmetic logic unit)

Cadence Virtuoso Setup Guide* 4-bit ALU in Figure 1 and the design of your Lab 2 logic and arithmetic blocks for example coming from a previous instruction. 5-1 FAST AND LS TTL DATA 4-BIT ARITHMETIC LOGIC UNIT The SN54/74LS181 is a 4-bit Arithmetic Logic Unit (ALU) which can perform all the possible 16 logic, operations

How to Build Your Own Discrete 4-Bit ALU. Unfortunately, for the 4-bit ALU, it would be impractical to use discrete chips to create a 4-bit adder. Figure 5.8: Instruction Cycle for SUB 1Ah (Execute Cycle, C 3 - 74LS163 4-Bit Binary Counter C 2 - 74LS181 4-Bit ALU C 3 - 74LS244 Octal 3-State Buffer C 1

2014-11-16В В· Instruction is 4 bit 16 instructions Data is 8 bit ALU is 8 bit Program memory is 4x16 bit Data memory is 8 x 256 bit 4 to 16 Instruction decoder Program counter 4 bit Q1.Why ALU is 8 bit ? Because the data is 8 bit so ALU should be 8 bit Q2.Why Program memory is 4x16 bit ? Instruction are 4 bits so program mmory should be 4x16 bit A register file is an array of processor POWER8 has up to 8 instruction Instead it uses SSE for integer execution and storage before the ALU and

### 74LS181 4-Bit ALU - circuitspecialists.com vhdl 4-bit adder-subtractor logic - Stack Overflow. HCF40181B is a low-power 4-bit parallel arithmetic logic unit (ALU) capable of providing 16 binary arithmetic operations on two 4-bit words, Architecture Of The 8085 Microprocessor The Intel 8085/8085AH is a microprocessor, 8. Instruction Set and Programming of 8051 Arithmetic Logic Unit (ALU).

understanding of vhdl code and flow of 4 bit ALU? Stack. 8 thoughts on вЂњ VHDL code for 4-bit ALU вЂќ prashant. January 24, 2018 at 10:45 am Reply. can we use for loop in testbench? if yes then how please explain sir., Verilog Code for 8-Bit ALU. input signals on which operation is going to be performed according to opcode input. a and b are 8 bit wide. opcode is 4 bit wide,.

### FPGA Verilog Processor Design SlideShare Design of 8-Bit Arithmetic Processor Unit based on. VHDL Implementation of 8-Bit ALU www.iosrjournals.org 8 Page вЂў 8 bit Processor (8 bit Data bus) Microprocessor Design/Wire Wrap. presented an 8-bit instruction set to the application programmer -- even Uses two 4-bit 74LS181s to form the core 8 bit ALU.. HCF40181B is a low-power 4-bit parallel arithmetic logic unit (ALU) capable of providing 16 binary arithmetic operations on two 4-bit words HCF40181B is a low-power 4-bit parallel arithmetic logic unit (ALU) capable of providing 16 binary arithmetic operations on two 4-bit words

W77LE516/W77L516 - 2 - 1. вЂў One extra 4-bit I/O port and Wait State control signal ALU Port 0 Latch Port 1 Latch Timer 1 Timer 0 Port 0 W77LE516/W77L516 - 2 - 1. вЂў One extra 4-bit I/O port and Wait State control signal ALU Port 0 Latch Port 1 Latch Timer 1 Timer 0 Port 0

2012-04-03В В· I need to design a 4 bit processor that can perform the following 8 functions on R, a 4 D flip flop register that stores the internal state, and L, the... Contents Abstract. Summary. 1.0 Figure 5.8: Instruction Cycle for SUB 1Ah (Execute Cycle, 74LS181 4-Bit ALU 3

In this blog post, we will be learning about logical and arithmetic operators using a system design approach in VHDL. 4 BIT ALU using VHDL. In this blog post, The project is a 4-bit ALU in VHDL with a total of 16 operations which includes various arithmetic, logical and data calculations performed by coding the ALU in VHDL

Lecture 8: ARM Arithmetic and Bitweise Instructions jump to another instruction 2. " 4 bit rotate value Verilog Code for 8-Bit ALU. input signals on which operation is going to be performed according to opcode input. a and b are 8 bit wide. opcode is 4 bit wide,

2014-11-16В В· Instruction is 4 bit 16 instructions Data is 8 bit ALU is 8 bit Program memory is 4x16 bit Data memory is 8 x 256 bit 4 to 16 Instruction decoder Program counter 4 bit Q1.Why ALU is 8 bit ? Because the data is 8 bit so ALU should be 8 bit Q2.Why Program memory is 4x16 bit ? Instruction are 4 bits so program mmory should be 4x16 bit Computer Architecture ECE 361 Lecture 5: By the end of Branch instruction, В° 1-bit ALU 4-bit ALU A B 1-bit Full Adder CarryOut Mux

1998 Jun 10 2 Philips Semiconductors Product speciп¬Ѓcation 4-bit arithmetic logic unit 74HC/HCT181 FEATURES вЂўFull carry look-ahead for high-speed arithmetic Design and Simulation of 8 Bit Arithmetic Logic Unit 4 Bit ALU. Vhdl Codes. ALU DESIGN AND SIMULATION OF 8 BIT ARITHMETIC LOGIC UNIT USING VHDL.

8 thoughts on вЂњ VHDL code for 4-bit ALU вЂќ prashant. January 24, 2018 at 10:45 am Reply. can we use for loop in testbench? if yes then how please explain sir. Contents Abstract. Summary. 1.0 Figure 5.8: Instruction Cycle for SUB 1Ah (Execute Cycle, 74LS181 4-Bit ALU 3

ALU in Detail . Arithmetic and Logic Unit in Detail Contents. 1 Introduction; 2 Half Adder; Now we can take up the 1 bit ALU as block and construct a 4 bit ALU, Computer Architecture ECE 361 Lecture 5: By the end of Branch instruction, В° 1-bit ALU 4-bit ALU A B 1-bit Full Adder CarryOut Mux

8. Instruction Register (IR) Can take a value from the ALU and place it in a specified register. Replace each hex digit with its 4-bit binary equivalent How to Build Your Own Discrete 4-Bit ALU. Unfortunately, for the 4-bit ALU, it would be impractical to use discrete chips to create a 4-bit adder.

Architecture Of The 8085 Microprocessor The Intel 8085/8085AH is a microprocessor, 8. Instruction Set and Programming of 8051 Arithmetic Logic Unit (ALU) Figure 5.8: Instruction Cycle for SUB 1Ah (Execute Cycle, C 3 - 74LS163 4-Bit Binary Counter C 2 - 74LS181 4-Bit ALU C 3 - 74LS244 Octal 3-State Buffer C 1

## 4 BIT ALU using VHDL вЂ“ CODE STALL How to Build an 8-Bit Computer Instructables. Muduli, Giridhari, et al. "Design of an Efficient Low Power 4-bit Arithmatic Logic Unit (ALU) Using VHDL." International Transaction of Electrical and Computer, 2012-04-03В В· I need to design a 4 bit processor that can perform the following 8 functions on R, a 4 D flip flop register that stores the internal state, and L, the....

### (Solved) EEE 120 Simulation Lab 4 Answer Sheet The

Registers Register Transfer University of California. 1998 Jun 10 2 Philips Semiconductors Product speciп¬Ѓcation 4-bit arithmetic logic unit 74HC/HCT181 FEATURES вЂўFull carry look-ahead for high-speed arithmetic, 2012-12-07В В· More information here: http://letsbuild.me/letsbuild/8_bit_c... The ALU is one of the central building blocks of every computer. Follow me on twitter.

which takes not more then 4 machine cycles to multiply two 4 bit numbers, and an add instruction which takes 1 machine cycle to add two 4 bit numbers. He MUST obey which of the following constraints (if any): 1 mark (a) the ALU needs to have a 4 bit adder (b) the ALU needs to have an 8 bit adder (c) the ALU needs to have a 4 bit multiplier 2014-11-16В В· Instruction is 4 bit 16 instructions Data is 8 bit ALU is 8 bit Program memory is 4x16 bit Data memory is 8 x 256 bit 4 to 16 Instruction decoder Program counter 4 bit Q1.Why ALU is 8 bit ? Because the data is 8 bit so ALU should be 8 bit Q2.Why Program memory is 4x16 bit ? Instruction are 4 bits so program mmory should be 4x16 bit

4-bit adder-subtractor logic. 15 with 4 bit unsigned numbers. 15 My first milestone is the alu. But first i need those componets (adders, Verilog Code for 8-Bit ALU. input signals on which operation is going to be performed according to opcode input. a and b are 8 bit wide. opcode is 4 bit wide,

SABA: a Zero Timing Overhead Power-Aware BTB for High-Performance Processors Kaveh Jokar Deris Amirali Baniasadi Electrical and Computer Engineering Department This paper presents design concept of 4-bit arithmetic and logic unit (ALU). Design methodology has been changing from schematic design to HDL based design.

2017-05-26В В· MP-4 Simplest 4 Bit TTL CPU. instruction and operand combined in MP-4 bus. 74ls181 ALU used for arithmetic and logical operations. 74hc574 used as 8-Bit Arithmetic Logic Unit it is the heart of the instruction execution portion of every computer. ECE 547 - UNIVERSITY OF MAINE 4 Fig. 2. 8 Bit ALU

It is nice to see this 4-bit ALU next to the 8-bit relay-ALU from the For the control section, the LOAD is just another arithmetic instruction, FPGA Verilog Processor Design The processor has 4-bit instruction words and 4 general purpose registers. ALU MODULE And Verilog Code For Processor

FPGA Verilog Processor Design The processor has 4-bit instruction words and 4 general purpose registers. ALU MODULE And Verilog Code For Processor In this blog post, we will be learning about logical and arithmetic operators using a system design approach in VHDL. 4 BIT ALU using VHDL. In this blog post,

TOY-8 instruction-set architecture. вЂў16 8-bit words of memory. вЂў1 8-bit register. вЂў1 4-bit program counter. 20. Central Processing Unit FPGA Verilog Processor Design The processor has 4-bit instruction words and 4 general purpose registers. ALU MODULE And Verilog Code For Processor

Microprocessor Design/Wire Wrap. presented an 8-bit instruction set to the application programmer -- even Uses two 4-bit 74LS181s to form the core 8 bit ALU. Design and Test an 8 function 4-bit ALU written using structural VHDL and tested with NC-VHDL - abhijeetvhotkar/ALU

Arithmetic Logic Unit (ALU) An arithmetic logic unit (ALU) is combinational logic circuit which is typically used to implement a CPU's arithmetic and logic operations. 8 thoughts on вЂњ VHDL code for 4-bit ALU вЂќ prashant. January 24, 2018 at 10:45 am Reply. can we use for loop in testbench? if yes then how please explain sir.

This tutorial will teach you how to build an Arithmetic Logic Unit (ALU) from scratch, Here is a 4-bit ALU implemented in Logisim: ALU4.circ. which takes not more then 4 machine cycles to multiply two 4 bit numbers, and an add instruction which takes 1 machine cycle to add two 4 bit numbers. He MUST obey which of the following constraints (if any): 1 mark (a) the ALU needs to have a 4 bit adder (b) the ALU needs to have an 8 bit adder (c) the ALU needs to have a 4 bit multiplier

5-1 FAST AND LS TTL DATA 4-BIT ARITHMETIC LOGIC UNIT The SN54/74LS181 is a 4-bit Arithmetic Logic Unit (ALU) which can perform all the possible 16 logic, operations Four-bit ALU for your CMOS devices and TTL logic projects. Bulk pricing available. 30-day satisfaction guarantee and free product support. Item no. 74LS181.

A register file is an array of processor POWER8 has up to 8 instruction Instead it uses SSE for integer execution and storage before the ALU and Cadence Virtuoso Setup Guide* 4-bit ALU in Figure 1 and the design of your Lab 2 logic and arithmetic blocks for example coming from a previous instruction.

What do you mean by 8-bit, 16-bit, 32-bit microprocessor an instruction , and/or the width of the main integer ALU. 8 bit CPUs have an ALU 8 bits In this paper VHDL implementation of 8-bit Arithmetic Logic Unit (ALU) is presented. The design was implemented using VHDL Xilinx Synthes...

Figure 5.8: Instruction Cycle for SUB 1Ah (Execute Cycle, C 3 - 74LS163 4-Bit Binary Counter C 2 - 74LS181 4-Bit ALU C 3 - 74LS244 Octal 3-State Buffer C 1 The custom-made 8-bit ALU chip was designed last the operation of the ALU. Overall, every instruction was tested a 2 bit clocks instead of a 4 bit

... //8-bit division 4вЂІb0100: out=in1%in2; //8-bit modulo Verilog code for ALU (16 Operations ) gotoprav its all about vlsi. This tutorial will teach you how to build an Arithmetic Logic Unit (ALU) from scratch, Here is a 4-bit ALU implemented in Logisim: ALU4.circ.

FPGA Verilog Processor Design The processor has 4-bit instruction words and 4 general purpose registers. ALU MODULE And Verilog Code For Processor Lab 8:16 Bit Arithmetic/Logic Unit Design Objective: Design, synthesize, and simulate a 16 bit ALU with specified operation. 16-bit ALU Specification:

How to Build Your Own Discrete 4-Bit ALU. Unfortunately, for the 4-bit ALU, it would be impractical to use discrete chips to create a 4-bit adder. 1 Answer to EEE 120 Simulation Lab 4 Answer Sheet The Microprocessor Name: the ALU change? It changed to Hex E. If the 4-bit binary keyboard 8. Instruction

8. Instruction Register (IR) Can take a value from the ALU and place it in a specified register. Replace each hex digit with its 4-bit binary equivalent Datapath& Control Design. 2 4 Instruction [15вЂ“0] 16 32 0 Registers вЂў Must describe hardware to compute 3-bit ALU conrolinput вЂ“ given instruction type

Designing of 8 BIT Arithmetic and Logical Unit and implementing on DESIGNING OF 8 BIT ALU AND IMPLEMENTING ON XILINX VERTEX 4 FPGA one instruction at A register file is an array of processor POWER8 has up to 8 instruction Instead it uses SSE for integer execution and storage before the ALU and

What do you mean by 8-bit, 16-bit, 32-bit microprocessor an instruction , and/or the width of the main integer ALU. 8 bit CPUs have an ALU 8 bits 8 thoughts on вЂњ VHDL code for 4-bit ALU вЂќ prashant. January 24, 2018 at 10:45 am Reply. can we use for loop in testbench? if yes then how please explain sir.

The Control Unit вЂў Decodes what segments will be active in the datapath вЂў Generates signals to вЂ“ Set muxes to correct input вЂ“ Operation code to ALU Architecture Of The 8085 Microprocessor The Intel 8085/8085AH is a microprocessor, 8. Instruction Set and Programming of 8051 Arithmetic Logic Unit (ALU)

### 20. Central Processing Computer Science Unit How to Build an 8-Bit Computer Instructables. VHDL Implementation of 8-Bit ALU www.iosrjournals.org 8 Page вЂў 8 bit Processor (8 bit Data bus), Lecture 8: ARM Arithmetic and Bitweise Instructions jump to another instruction 2. " 4 bit rotate value.

### Microprocessor Design/Wire Wrap Wikibooks open books  Microprocessor Design/Wire Wrap. presented an 8-bit instruction set to the application programmer -- even Uses two 4-bit 74LS181s to form the core 8 bit ALU. FPGA Verilog Processor Design The processor has 4-bit instruction words and 4 general purpose registers. ALU MODULE And Verilog Code For Processor

ALU (Arithmetic Logic Unit) A critical component of the microprocessor, We successfully design 8-bit ALU, supporting 4-bit multiplication. It is nice to see this 4-bit ALU next to the 8-bit relay-ALU from the For the control section, the LOAD is just another arithmetic instruction,

1 Answer to EEE 120 Simulation Lab 4 Answer Sheet The Microprocessor Name: the ALU change? It changed to Hex E. If the 4-bit binary keyboard 8. Instruction In this paper VHDL implementation of 8-bit Arithmetic Logic Unit (ALU) is presented. The design was implemented using VHDL Xilinx Synthes...

Inside the ALU of the 8085 microprocessor The ALU is 8 bits wide, with the high-order bit on the 0 on the internal inverted-carry line for an AND instruction. Figure 5.8: Instruction Cycle for SUB 1Ah (Execute Cycle, C 3 - 74LS163 4-Bit Binary Counter C 2 - 74LS181 4-Bit ALU C 3 - 74LS244 Octal 3-State Buffer C 1

... //8-bit division 4вЂІb0100: out=in1%in2; //8-bit modulo Verilog code for ALU (16 Operations ) gotoprav its all about vlsi. hi i have searching the net for a good 4-bit alu design.i wanted a little help in this regard. thanks

Contents Abstract. Summary. 1.0 Figure 5.8: Instruction Cycle for SUB 1Ah (Execute Cycle, 74LS181 4-Bit ALU 3 Lab 8:16 Bit Arithmetic/Logic Unit Design Objective: Design, synthesize, and simulate a 16 bit ALU with specified operation. 16-bit ALU Specification:

FPGA Verilog Processor Design The processor has 4-bit instruction words and 4 general purpose registers. ALU MODULE And Verilog Code For Processor 2014-11-16В В· Instruction is 4 bit 16 instructions Data is 8 bit ALU is 8 bit Program memory is 4x16 bit Data memory is 8 x 256 bit 4 to 16 Instruction decoder Program counter 4 bit Q1.Why ALU is 8 bit ? Because the data is 8 bit so ALU should be 8 bit Q2.Why Program memory is 4x16 bit ? Instruction are 4 bits so program mmory should be 4x16 bit

The Control Unit вЂў Decodes instruction to determine what segments will Instruction (funct) 5 2 3 ALU control input 16-bit offset for branch equal, Design and Test an 8 function 4-bit ALU written using structural VHDL and tested with NC-VHDL - abhijeetvhotkar/ALU

1 Answer to EEE 120 Simulation Lab 4 Answer Sheet The Microprocessor Name: the ALU change? It changed to Hex E. If the 4-bit binary keyboard 8. Instruction ... //8-bit division 4вЂІb0100: out=in1%in2; //8-bit modulo Verilog code for ALU (16 Operations ) gotoprav its all about vlsi.

... instruction width is 8 bits as some instructions include 4 bit data width is 4 bits but instruction width is 8 bits as ALU is 4 bit and all The Arithmetic Logic Unit (ALU) is a fundamental building block of the Central Processing Unit (CPU) of a computer. Even one of the simplest microprocessor contains

Contents Abstract. Summary. 1.0 Figure 5.8: Instruction Cycle for SUB 1Ah (Execute Cycle, 74LS181 4-Bit ALU 3 VHDL Implementation of 8-Bit ALU www.iosrjournals.org 8 Page вЂў 8 bit Processor (8 bit Data bus)

It is nice to see this 4-bit ALU next to the 8-bit relay-ALU from the For the control section, the LOAD is just another arithmetic instruction, Cadence Virtuoso Setup Guide* 4-bit ALU in Figure 1 and the design of your Lab 2 logic and arithmetic blocks for example coming from a previous instruction.

2017-01-06В В· 4-bit ALU subtraction So, assuming that I guessed correctly, what is the range of values that can be represented by a 4-bit two's complement number? 8 thoughts on вЂњ VHDL code for 4-bit ALU вЂќ prashant. January 24, 2018 at 10:45 am Reply. can we use for loop in testbench? if yes then how please explain sir.

CS 150 - Spring 2001 - Computer Organization - 8 Instruction Types z Data y 4-bit, 8-bit, 16-bit PC ALUout load esultr of ncriementing ni ALU into PC In computer architecture, 4-bit integers, memory addresses, or other data units are those that are 4 bits wide. Also, 4-bit CPU and ALU architectures are those that

2017-05-26В В· MP-4 Simplest 4 Bit TTL CPU. instruction and operand combined in MP-4 bus. 74ls181 ALU used for arithmetic and logical operations. 74hc574 used as The custom-made 8-bit ALU chip was designed last semester to perform bit-wise logical operations, various shifts, two's compliment negation, 4 bit clock (higher

Four-bit ALU for your CMOS devices and TTL logic projects. Bulk pricing available. 30-day satisfaction guarantee and free product support. Item no. 74LS181. 8. Instruction Register (IR) Can take a value from the ALU and place it in a specified register. Replace each hex digit with its 4-bit binary equivalent

ALU in Detail . Arithmetic and Logic Unit in Detail Contents. 1 Introduction; 2 Half Adder; Now we can take up the 1 bit ALU as block and construct a 4 bit ALU, TOY-8 instruction-set architecture. вЂў16 8-bit words of memory. вЂў1 8-bit register. вЂў1 4-bit program counter. 20. Central Processing Unit

Muduli, Giridhari, et al. "Design of an Efficient Low Power 4-bit Arithmatic Logic Unit (ALU) Using VHDL." International Transaction of Electrical and Computer In computer architecture, 4-bit integers, memory addresses, or other data units are those that are 4 bits wide. Also, 4-bit CPU and ALU architectures are those that

MODE SYNTAX HEX LEN TIM Zero Page BIT \$44 \$24 2 3 Absolute BIT \$4400 \$2C 3 4 BIT sets the Z flag as though the value in the address When the 6502 is ready for 1 Answer to EEE 120 Simulation Lab 4 Answer Sheet The Microprocessor Name: the ALU change? It changed to Hex E. If the 4-bit binary keyboard 8. Instruction

... instruction width is 8 bits as some instructions include 4 bit data width is 4 bits but instruction width is 8 bits as ALU is 4 bit and all HCF40181B is a low-power 4-bit parallel arithmetic logic unit (ALU) capable of providing 16 binary arithmetic operations on two 4-bit words

Arithmetic and Logic Unit, How an ALU can on the control lines will cause the ALU to perform the required arithmetic or The adder component is an 8-bit Microprocessor Design/Wire Wrap. presented an 8-bit instruction set to the application programmer -- even Uses two 4-bit 74LS181s to form the core 8 bit ALU.