Introduction to the COSMAC Elf from PCBWay Building the COSMAC Elf from PCBWay is a quick, and inexpensive way to learn the COSMAC 1802. This is another project by Mr. Lunde. You can order the boards at this link. You will likely want to get the main processor (CPU) board, Read More »
Introduction to the Cosmac Elf Control Circuit The Cosmac Elf Control Circuit allows you to enter a program through the front panel switches. There are a few things that need to happen to make this circuit work properly. In this section, we’ll go over each component, and I’ll explain the Read More »
Introduction to the 1802 Membership Card Timer In this section, we’ll crate a scan based 1802 Membership Card Timer using BASIC3. The 1802 Membership card uses the COSMAC 1802 Processor. Since we are basing the timer on the scan rate, you may have to vary the delay loops to calibrate Read More »
Introduction to COSMAC 1802 I/O Operations COSMAC 1802 I/O Operations allow us to get data from an input port, and write data to an output port. In this case, I’m using the 1802 membership card. On the 1802 Membership Card, we use Port 4 for both the switches and the Read More »
Introduction to Inverting Q on the ELF MC Certain firmware requires Inverting Q on the ELF MC (1802 ELF Membership Card). This is usually true when you have the front panel attached, which is revision J or later. In my case, I wanted to run Diskless ELF/OS (and still have Read More »
Introduction to Building the Elf Membership Card Building the Elf Membership Card takes about a half day, although I always tell everyone to plan on twice that amount of time. Don’t get into a rush when building these projects! Always allow for plenty of breaks to think about your next Read More »
Introduction to COSMAC 1802 OR & AND Statements COSMAC 1802 OR & AND instructions allow us to manipulate data. These instructions work on all 8 bits of a word at a time. These instructions work just like standard bit level logic gates work. They just perform the operation bit by Read More »
Introduction to COSMAC 1802 Subroutines We use COSMAC 1802 Subroutines to execute a specific set of instructions. For example, we might have a subroutine that causes a delay every time we execute it. You could also have a subroutine that converts Celsius to Fahrenheit, or vice versa. We might call Read More »
Introduction to COSMAC 1802 Basic Branching COSMAC 1802 Basic Branching instructions allow you to execute different parts of code based on certain conditions. These conditions might include inputs that are high, or results of an operation that return a zero value, negative value, etc. In this section, we’ll cover the Read More »
Introduction to COSMAC 1802 Subtract Instructions COSMAC 1802 Subtract Instructions will subtract the accumulator (D Register) from an immediate value, or a memory location (or vice-versa) In this post, we’ll go over each of these instructions, and how you would use them in your logic. There are eight subtract instructions Read More »
