In this project
The 74LS181 IC is an arithmetic logic unit / function generator IC that has a complexity of 75 congruent gates on a monolithic IC chip. These circuits perform 16 binary arithmetic operations on two 4-bit words. These operations are selected by the four function-select lines (S0, S1, S2, S3) and include addition, subtraction, decrement, and straight transfer. The 74LS181 IC also constitutes a wide array of features such as thermal overload protection & ESD protection. The IC 74LS181 is smaller in size and it has a much faster speed which makes it reliable in every kind of device. The design concentrates on the chip to be used in high-performance applications such as memory-decoding.
What is an ALU/Function Generator?
The arithmetic logic unit (ALU) is a combinational digital circuit that performs arithmetic and bitwise operations on integer binary numbers. It performs a variety of arithmetic & logical operations on its inputs (better known as operands) such as simple addition, subtraction, multiplication, division, and logic operations, such as OR and AND. The control unit (CU) fetches the instructions & operative data from the memory and uses operations of the ALU to carry out those instructions using that data.
74LS181 Pinout
74LS181 Pin Configuration
| Pin No | Pin Name | Description |
|---|---|---|
| 1 | B0' | Active low Operand Input B0' |
| 2 | A0' | Active low Operand Input |
| 3 | S3 | Function Select Input S3 |
| 4 | S2 | Function Select Input S2 |
| 5 | S1 | Function Select Input S1 |
| 6 | S0 | Function Select Input S0 |
| 7 | Cn | Carry Input |
| 8 | M | Mode Control Input |
| 9 | F0' | Function Output F0' |
| 10 | F1' | Function Output F1' |
| 11 | F2' | Function Output F2' |
| 12 | GND | Ground Pin |
| 13 | F3' | Function Output F3' |
| 14 | A=B | Comparator Output |
| 15 | P' | Active low carry propagate |
| 16 | Cn+4 | Carry Output |
| 17 | G' | Active low carry generator |
| 18 | B3' | Active low Operand Input B3' |
| 19 | A3' | Active low Operand Input A3' |
| 20 | B2' | Active low Operand Input B2' |
| 21 | A2' | Active low Operand Input A2' |
| 22 | B1' | Active low Operand Input B1' |
| 23 | A1' | Active low Operand Input A1' |
| 24 | VCC | Chip Supply Voltage |
74LS181 Features & Specifications
- Technology Family: LS
- Rating: Catalog
- Balanced propagation delays
- Designed specifically for high speed
- Product type: Standard
- Provides 16 Arithmetic Operations Add, Subtract, Compare, Double, Plus Twelve Other Arithmetic Operations
- Provides all 16 Logic Operations of Two Variables Exclusive OR, Compare, AND, NAND, OR, NOR, Plus Ten other Logic Operations
- Full Lookahead for High Speed Arithmetic Operation on Long Words
- Input Clamp Diodes
- VCC (min): 4.75V
- VCC (max): 5.25V
- Typical propagation delay: 21nS
- Low power consumption: 32mW
- ESD protection
- Operating temperature: 0ºC to 70ºC
Applications
- In computer system architecture design, When operative speed requirements are not stringent, it can be used to serve in a simple ripple carry mode by connecting the Carry output (Cn+4) signal to the Carry input (Cn) of the next unit.
- For high speed operation, the IC is used in conjunction with the 9342 or 93S42 carry look ahead circuit.
You can download this datasheet for 74LS181 4-Bit Arithmetic Logic Unit IC from the link given below:
See Also: 74LS164 8-Bit Shift Register IC With Parallel Outputs – Datasheet | 74LS157 Quad 2 To 1 Line Multiplexer IC – Datasheet | 74LS132 Quad 2-Input Schmitt trigger NAND Gate IC – Datasheet
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