Hi Mike,

If I understand you correctly, you're saying that adding the buffer chips will make it easier to lay out your circuit on a single sided board. Also, I think you said earlier that you plan to have the buffers enabled all the time.

If you back away two steps and take a deep breath, I think you'll see that what you're really suggesting is the use of the buffer chip as an IC package full of junpers! Right?

As others have said, you can do that. But why bother? If you need jumpers, use jumpers, for a multitude of really good reasons:

• A little piece of wire is way more reliable than an IC.


• A little piece of wire is free.


• With a little piece of wire, you don't have to worry about "the output being the same as the input".


• You don't have to route power and ground connections to a little piece of wire.


• You don't need a decoupling capacitor with a little piece of wire.


• Little pieces of wire will be much more effective than an IC package full of buffers in solving your layout problems because you'll be able to put the little pieces of wire wherever you want on the board. With an IC package full of buffers, you're just handicapping yourself from the beginning because you have to live with the configuration of the package and the pinout of the device.

If you somehow don't like the idea of "little pieces of wire", maybe you could use zero-ohm resistors. They'd look more like official electronic components and give you most of the advantages of little pieces of wire except they're not free.

Another suggestion: I think you're trying to take too big a step by making a printed circuit board for a design that you're not even sure is correct. I think you should take two more steps back and consider making a prototype using wire wrap or some other breadboarding method where you can build up your circuit one step at a time, test it at each step of the way, and easily make changes when you need to. For example:

1. Wire up power, ground, a decoupling cap, EA, and the crystal (and its caps). Check that the part oscillates and that ALE wiggles like it should. If there are problems, solve them and fix them before moving on to the next step.


2. Add the address latch and program memory and try to run the simplest program that you can write that does nothing more than wiggle an I/O pin. If there are problems, solve them and fix them before moving on to the next step.


3. Etc., etc., etc.


4. When you know that your circuit is correct, then worry about laying out and making a printed circuit board.

Another suggestion: If you don't have an oscilloscope, get one. Others may disagree on this point, but I don't think you will ever get very far without being able to actually see what your circuit is doing. Without a 'scope, it's all just guesswork. It looks like you can get decent, used 'scopes any day of the week on eBay for less than $100.

-- Russ

Take small steps. More of them will be successful, and those that aren't won't be so painful.