First RegFile board complete

A project log for ECM-16/TTL homebrew computer

16 bit Computer made from ttl logic chips

PavelPavel 04/21/2021 at 12:490 Comments

The first board done for the register file is the selector for the output, which is to be used as Src2 input to ALU. This is conceptually most simple and most familiar part, as the similar board was already been built for the ALU.

Hire is the new board:

Plans for the future:

Next will be similar board, selector for ALU Src1 input. It will also have additional tri-state output meant to be the output directly to the data bus, which is needed for reg-reg transfers (MOV operations) and for storing data to memory. This independent output from register file to bus, circumverting the ALU is not strictly necessary, but is desirable in view of reducing propagation delays.

On the whole RegFile, regarding creation of single interface board similar to the one for ALU, I think it still an OK idea. I am not yet sure how it will look like, only that it will be integrated with register display. 

As for Register Display -- I want to see the contents of all registers at a glance. But not only contents, but also the indication of which registers are selected to outputs as well as to which of the registers is being written. I gather, this has good aesthetics (all the blinky lights) in addition to strictly functional role of being able to monitor and tracking instruction execution. It could be particularly helpful at the commissioning stage, to ensure all instructions work as desired.

Here is schematic view of what this display is going to be: