EdSim51 alternative: from the 8051's programs to the logic inside a CPU
EdSim51 (EdSim51DI) is a free educational simulator for the 8051 microcontroller by James Rogers, now at version 2.1.39. You write or load 8051 assembly, single-step it, and watch the registers, the data and code memory and all 32 port pins, while a virtual training kit reacts on the ports: an ADC and a comparator, a UART, four multiplexed 7-segment displays, a 4 by 3 keypad, 8 LEDs, 8 switches, a DC motor and a DAC shown on an oscilloscope. It is written in Java, so it needs a Java runtime, and it is downloaded as a zip file. Its site also offers a companion textbook and the EdX51 operating system. EdSim51 is a virtual 8051 training kit for writing embedded programs; digiwleea has you build the computer's hardware itself, gate by gate.
What EdSim51 is good at
Learning 8051 assembly and embedded programming without hardware: start with the move, arithmetic and branch instructions, then write code to scan a keypad, count a motor's revolutions or multiplex the 7-segment displays, and see every port pin change as you step. Some peripherals share port pins, so students also learn to juggle them, as on a real board. For an 8051 course, it is a classic. (digiwleea is an independent project, not affiliated with EdSim51 or its author.)
How digiwleea is different
digiwleea is not an 8051 simulator and does not run 8051 code. It is about the hardware underneath: in the browser, with nothing to install, you build NOT and NAND from CMOS transistors, then adders, an ALU, latches, registers, RAM, a program counter and a control unit, through a 40+ level course where every part is checked against its truth table, with an AI tutor (Wleea). The CPU you finish with is a small 8-bit accumulator machine whose capstone runs a stored LOAD, ADD, STORE, HALT program. EdSim51's 7-segment displays and keypad have their logic counterparts here too: the BCD to 7-segment decoder and the priority encoder.
| EdSim51 | digiwleea | |
|---|---|---|
| Focus | Programming the 8051 and its peripherals | Digital logic from transistors to a simple CPU |
| The processor | A given 8051, with registers, memory and ports | Built by you: a small 8-bit accumulator machine |
| Peripherals | Keypad, displays, LEDs, motor, UART, ADC, DAC | Displays and I/O parts in the lab |
| Runs on | Desktop, with a Java runtime | Any modern browser |
| Price | Free (not to be sold for profit) | Free lab and Act I; Premium for the full course |
No sign-up is needed to start: open the lab and place your first transistor, or read the free theory course. The account (and the AI tutor) are optional.
More comparisons: CPU and assembly simulators
See for yourself: build a logic gate from transistors in the simulator, then follow the path from sand to an 8-bit CPU.
Open the digiwleea lab →Frequently asked
Is EdSim51 free?
Yes. Its site says EdSim51 and EdSim51DI are available free of charge, and may not be sold for profit or bundled into a product sold for profit without written permission from James Rogers.
What do I need to run EdSim51?
A Java runtime. EdSim51 is written in Java and downloaded as a zip file; its installation page covers Windows and Ubuntu and says it should run on any system with Java.
Is there an online 8051 simulator in the browser?
EdSim51 itself is a desktop Java program. digiwleea runs in the browser but is not an 8051 simulator: it teaches the logic inside a processor by having you build one.