The 74181 ALU (arithmetic/logic unit) chip powered many of the minicomputers of the 1970s: it provided fast 4-bit arithmetic and logic functions, and could be combined to handle larger words, making it a key part of many CPUs. But if you look at the chip more closely, there are a few mysteries. It implements addition, subtraction, and the Boolean functions you'd expect, but why does it provide several bizar ...

A computer's arithmetic-logic unit (ALU) is the heart of the processor, performing arithmetic and logic operations on data. If you've studied digital logic, you've probably learned how to combine simple binary adder circuits to build an ALU. However, the 8008's ALU uses clever logic circuits that can perform multiple operations efficiently. And unlike most 1970's microprocessors, the 8008 uses a complex car ...

What's inside a TTL chip? To find out, I opened up a 74181 ALU chip, took high-resolution die photos, and reverse-engineered the chip.1 Inside I found several types of gates, implemented with interesting circuitry and unusual transistors. The 74181 was a popular chip in the 1970s used to perform calculations in the arithmetic-logic unit (ALU) of minicomputers. It is a moderately complex chip containing abou ...

The DueProLogic makes programmable logic easy with an all inclusive development platform. It includes an Altera Cyclone IV FPGA, on board programming, four megabit configuration flash, and an SD connector for add on memory. You can create your HDL code, program it into the flash and interact with the hardware via a Windows PC. This is the FPGA (Field-Programmable Gate Array) development board and runtime en ...

The accuracy of any circuit or system that uses a thermocouple to determine the temperature of a process is limited by the accuracy of the method used to perform cold-junction compensation. In a thermocouple measurement, two wires of dissimilar metal join together at the "hot," or measurement, junction. The isothermal termination of the thermocouple wires provides a second "cold," or reference, junction. Th ...

The Arduino Gatekeeper is an IoT-connected authenticator for outdoor gates and doors. No longer are keys required for secure backyards! Things used in this project Story Introduction The Arduino Gatekeeper is an IoT-connected authenticator for outdoor gates and doors (or anything else that can be monitored with reed switches). The first function of the device is to remotely monitor when gates are opened or ...

I stood in stunned silence at the smoke billowing up from the hardware on the workbench. Just moments before, it had been operating as expected, before self-destructing with a sound that can only be compared with a gunshot. The failure of the hardware under test had an unexpected consequence: the computer that had been using a USB-to-UART converter to communicate with the hardware experienced a USB fault th ...

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