REV2 8 Bit Hex to Dec - Bin to BCD

270

03:22:54

With the increase in workspace, I decided to review my past circuits to see if I could improve the simulation experience.

This is a hexadecimal to decimal and/or a binary to BCD (Binary Coded Decimal) converter using the Double-Dabble algorithm.  As an example, it converts "3D" Hex (0011 1101 binary) to "61" Dec (0110 0001 BCD).  See the first versions here:  
4 bit:   https://everycircuit.com/circuit/6548980953251840.  
8 bit:  https://everycircuit.com/circuit/6747473873469440.
They work, but I want to try and improve them.

My objectives are:
1) Remove D-Type flip-flops:  They seemed to cause much of the slow loading and lag.  I replaced them with counters/registers, which seemed to help a lot.

2) Increase speed:  This circuit is about 3 times faster than the original (and that's still kinda slow).

3) Reduce component numbers:  The binary serial stream circuit is more efficient.  I also saved on the reset logic by using the RESET pin on the counters. 

Still, this circuit is not running as fast as I would like.  Does anyone know why?  The whole circuit boils down to just a very large Moore State Machine with 10 state variables (counter outputs).  The boolean Next State Equations are created with the logic gates.  Shouldn't this be very fast for a circuit engine to solve?

Can anyone help me with my objectives?

published 1 year ago

jason9

1 year ago

I don’t really know how to make this faster. Unfortunately, EC has a somewhat complicated logic gate model that includes things like gate transition delay which complicates the sim a lot more than a simple binary on/off output like the counters use. The only ways I can think of to speed up the sim are to replace the gates with something faster like more counters or even discrete transistors.

592azy2circuitdude

1 year ago

First, thanks, Jason, for taking the time to look into this. I didn't realize the propagation delay and logic gate model would slow down the simulation so much. But I'm inclined to agree.

592azy2circuitdude

1 year ago

I tried to run some speed tests, and I think the number of nodes a circuit contains may be a larger factor in determining run speed. For instance, try removing the 7-segment displays and 7-segment decoders. The lag becomes almost gone!

jason9

1 year ago

Oh, that’s interesting. I didn’t expect that. Seems like those components are pretty laggy, presumably due to the number of nodes involved. In that case there may not be much that can be done.

add comment in editor

EveryCircuit is an easy to use, highly interactive circuit simulator and schematic capture tool. Real-time circuit simulation, interactivity, and dynamic visualization make it a must have application for professionals and academia. EveryCircuit user community has collaboratively created the largest searchable library of circuit designs. EveryCircuit app runs online in popular browsers and on mobile phones and tablets, enabling you to capture design ideas and learn electronics on the go.