My CPU

Fun CPU is a seven bit homebrew processor with unique, unconventional design to natively support functional programming in machine language. FunCPU employs a tagged architecture, but does not have registers, of which contents are exposed to the programmer. Sure, it has some internal registers, but…

The ALU module is very simple and straightforward. It is mounted together with the control board encoding logic on a single board. It performs a simple addition operation on the two operands as described in the following table. The two selector bits define the two input sources. ALU…

Construction of FunCPU has begun with the clock generator. The module is already fully functional on its own, but space is left for incorporating more components for the EPROM chips storing the micro-program and for some control logic.   An 555 is used to generate the base for the clock…

Now let us take a look at how the functional CPU (FunCPU for short) can be programmed in reality, from the programmer’s point of view.   This will be covered by looking at each gizmo  (i.e. button, switch, LED, etc.) on the front/control panel. On the bottom right side, the purpose of the…

It is not trivial how to handle argument passing in the lack of stack, or any dedicated storage for parameters. Consider the following examples: fac (n):= n*fac(n-1) fac(add(2,3))? ack(add(fac(fac(2)+fac(1)),fac(1)),1)? I wanted a simple solution, which still works without posing serious…

When evaluating expressions, the CPU must exactly know how to evaluate an expression, what function/expression parts should be evaluated first, next, and last etc. Therefore the representation of expressions and functions must be unambigous with respect to parenthesis and priorities. In…

In the previous post we have seen how 8 bit symbols represent literals, arguments, functions, etc. Similarly, it was vital to have a good and efficient function encoding. Basically in the context of function encoding we need to be able to answer the following question: Where does the function…

FunCPU will operate with 7-bit numerals (to understand why see the next couple of posts) and will directly support the following built-in functions: inc(x) is used for incrementing a value, that is for any x: x+1=inc(x). dec(x) is used for decrementing a value in the similar fashion. if-then-else…