65C816 Memory Maping

[Dimitri]

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

[GARTHWILSON]

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.

[DerTrueForce]

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.

[GARTHWILSON]

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