Misc and Barrel rotator boards are complete

A project log for ECM-16/TTL homebrew computer

16 bit Computer made from ttl logic chips

PavelPavel 03/01/2021 at 08:210 Comments

Since the last update I've soldered , assembled and tested two new boards -- one containing multiple functions, and other - barrel rotator, which performs arbitrary bit rotations of 16-bit words.

Miscellaneous components board

Here is overall scheme of ALU, with components on the Misc board are in shaded area:

The components take from 3 (zero detector) to 7 (shifter) chips, so all of them were possible to place on single board.

Here is the board itself:

Barrel Rotator board

The barrel rotator performs word rotations to the left by an amount ranging from 0 to 15 bits, in one clock cycle. This module is useful for operations like swapping bytes in the word, or for speed-up of operations involving floating point numbers. 

It is constructed as 4 levels of 16-bit 2-to-1 multiplexers, each level multiplexing increasingly disparate bits, here is the schematic:

and the actual board looks like this:


For ALU completion, only one board is left to be completed -- the 16-bit 8-to-1 multiplexer, which will select one of the outputs from previously created boards.

After that  I'll start working on the Register File, and beginnings of the control module.