Content for 74LS139


The LSTTL/MSI SN54/74LS139 is a high speed Dual 1-of-4 Decoder/Demultiplexer. The device has two independent decoders, each accepting two inputs and providing four mutually exclusive active LOW Outputs. Each decoder has an active LOW Enable input which can be used as a data input for a 4-output demultiplexer. Each half of the LS139 can be used as a function generator providing all four minterms of two variables. The LS139 is fabricated with the Schottky barrier diode process for high speed and is completely compatible with all Motorola TTL families.

Raspberry Pi CPU Temperature Indicator

“Previously I had introduced simple raspberry pi (Hereinafter as RPI) operational status indicator circuit. This time, Ill explain some more useful indicator circuit for RPI running as headless (without monitor) manner. The circuit above shows CPU temperature into 4 different …

SAP-1 Processor Architecture

“A simple 8-bit micro-processor using mostly discrete logic chips. This project is mostly based on the 8-bit Breadboard computer by Ben Eater Banner Specs ~400 Hz Clock 8-bit Data Bus 16-bit Control Word 5 Microsteps per Instruction 16 byte RAM …

Build an 8-bit computer from scratch

“I built a programmable 8-bit computer from scratch on breadboards using only simple logic gates. I documented the whole project in a series of YouTube videos and on this web site. “

Visualizing ROMs 1: Diode Matrix ROM

“To start with, ROMs come in a few different varieties. The most well known are EPROMs. These are ICs with a quartz window on the top, through which you can see the storage array on the silicon. This window is …