System fundamentals – Geronimo/370

Retro Z80 computer (9) – BLINKENLIGHTS

Posted on2022-01-212022-01-21

A small project today. I added ‘BLINKENLIGHTS’ to my Z80. This term stems from an old sign that used to hang in computer rooms: ACHTUNG!ALLES TURISTEN UND NONTEKNISCHEN LOOKENSPEEPERS!DAS KOMPUTERMASCHINE IST NICHT FÜR DER GEFINGERPOKEN UND MITTENGRABEN! ODERWISE IST EASY TO SCHNAPPEN DER SPRINGENWERK, BLOWENFUSEN UND POPPENCORKEN MIT SPITZENSPARKEN.IST NICHT… Read the rest

Video series about SCEPSIS

Posted on2019-07-182019-07-18

I’m in the process of producing a viedo series about my Simple CPU emulator, SCEPSIS. You can find the expaning playlist here: playlist for SCEPSIS videos… Read the rest

SCEPSASM – The SCEPSIS Assembler

Posted on2019-06-202019-06-20

SCEPSASM is an assembler that will – based on a language definition (langdef) file – parse a source file and convert it into an object memory file that can be executed with the SCEPSIS emulator. The SCEPSASM main screen The current version works and it’s output OBJect files will be… Read the rest

SCEPSIS

Posted on2019-05-252019-06-113 Comments

Have a look at my new project, the ‘Simple CPU Emulation Program (Student Instruction System)‘… SCEPSIS control panel… Read the rest

8 bit computer, progress on the Control Unit

Posted on2017-10-18

8 bit computer, progress on the Control Unit Below some pictures of the progress of the construction of the Control Unit of my 8 bit computer. Two pictures, one of the front and one of the back. I’m not satisfied with the layout, and I think I am going to… Read the rest

8 bit computer, solution for the microcode

Posted on2017-10-09

8 bit computer, solution for the microcode As I mentioned in this post, I was looking for a solution to program a couple of EEPROMs that are going to hold the microcode for my 8 bit computer. Using an Arduino Nano, I created a solution that also uses a python… Read the rest

8 bit computer, storing the microcode, solution

Posted on2017-09-30

8 bit computer, storing the microcode, solution I have a solution for the micro code predicament mentioned before. I’m using an 8KB EEPROM memory chip (the AT28C64). These memory chips will be divided into four segments, each holding pieces of microcode. Decoding instructions This microcode will be addressed as follows:… Read the rest

8 bit computer, microcode challenges

Posted on2017-09-24

8 bit computer, microcode challenges My 8 bit instructions can have up to 8 microcode steps each; I defined up to 24 control signals (thus needing 3 bytes per step); So in the Arduino Nano I’m using, I have to define them as uint32_t variables (which are 4 bytes long).… Read the rest

8 bit computer, output module, problem solved

Posted on2017-09-24

8 bit computer, output module, problem solved Remember that annoying problem I spoke of? I solved it! It appears I had soldered two connections together by accident. Almost invisible, but still two outputs were connected, resulting in double displays on the two leftmost 7-segment displays. Fortunately I was able to… Read the rest

8 bit computer, instructions and microcode

Posted on2017-09-232019-05-12

When designing and building your own computer, you have to design and build your own instruction set as well. So that’s one of the things I’m doing right now. One of the functions of the Control Unit in the computer is to decode the instructions and have all the chips… Read the rest

8 bit computer, buildup status

Posted on2017-09-21

8 bit computer, buildup status The status so far in pictures: … Read the rest

8 bit computer, Output Module complete

Posted on2017-09-16

8 bit computer, Output Module complete Today I finished building and testing the Output Module for my 8 bit computer. See video and picture below. … Read the rest

8 bit computer, test the Output Module

Posted on2017-09-09

8 bit computer, test the Output Module Today I hooked up my Output module – still on breadboard – to the signals from the PCB modules. As you can see in the video below, it works so far. At first, the clock pulse was very messy, but adding a 100nF… Read the rest

8 bit computer, ALU complete

Posted on2017-08-27

8 bit computer, ALU complete Everything is connected now on the ALU board. the bus has been connected (blue wires) the A register is connected to the ALU chips (purple wires) the B register is connected to the ALU chips (green wires) the ALU output is connected to the connector… Read the rest

8 bit computer, building up the ALU

Posted on2017-08-20

8 bit computer, building up the ALU The ALU Building up the heart of the computer, the two big chips are 74LS181’s (4 bit ALU’s, hence there’s two of them). The two little chips below them are the 74LS245 tri-state buffer, that connects it to the bus in a controlled… Read the rest