So long time no see. Life got severely in the way. Have a step-daughter, and ex-live in, now a wife, and two kids of my own LOL.

Was going over my notes for what I wanted to build, and been trying to map the memory of the board, so far I have it down to the two attachments. Logic wise it works, based on this simulator, but doesn't mean it would work in circuit. Worried about propagation time.

Made up of 3 74'154, 1 4075 triple OR Gate, 1 74'10 NAND, and 2 NOT gates.





Any thoughts?

And yes I realized I wasted a whole bunch of address space in the I/O region, but I figured a single 32kb RAM chip, and a 16kb EEPROM makes it easy to do chip selects, so just went with it to simplify my addressing scheme.

Dimitri

Be sure to look at the propagation delays of the 4000-series IC. 4000's are good when you need 12V logic or other high-ish voltage and can tolerate really slow logic. At 5V, they're slower than molasses in January. You have a couple of places where there are two of these cascaded. I do wish the '154 were available in 74AC; but alas, no cigar.

_________________
http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

As Mr. Wilson says, 4000-series logic is generally a bit slow for this type of purpose.
The usual recommendation is to use HC or AC logic for better power consumption and speed.
A quick search indicates that the 74xx154 and 74xx10 are available in HC, and that the 74HC4075 is a triple 3-input OR.

The 74HC4xxx will have HC speeds. 4000 series without the 74xx in front will be really slow though.

_________________
http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?