Here are a few Frequently Asked Questions  about the TNC project.

Bob Ball has passed most of these along but I may add to the list as our club members build a few of these .


How in the world does the reset vector get set?

How long will bloader remain on the chip?

Does EERAM get cleared by bloader?

What kind of  resistors are these with 5 color bands? NEW 4-14-2005













How in the world does the reset vector get set ?

When you put bloader in the chip, it puts it's startup vector in location 0. When a reset occurs it then jumps to high memory to execute bloader. Bloader in executing then determines if Screamer is on the link. If it is, it prepares for a download. If not, it jumps to location 0x2. So question is, how does the starting address of the users program get in 0x2?? Well, bloader does it. When it loads a user's program, it copies the vector that supposed to go into location 0 and sticks it in 0x2 instead. So, it will work with any program, as long as the starting vector is in location 0 (which is normal).


How long will bloader remain on the chip? 

Answer is .. virtually forever UNLESS the chip happens to get reset (via MCLR) in the middle of the load sequence. That is why I disabled the MCLR enable and why I use some hefty filter caps to make the 5V on/off is smooth on power up/down. With this done, I have been using it almost a year now with many, many loads and it still works fine


Does EERAM get cleared by bloader??

No, all your station options will remain OK after a reprogram by bloader.


What kind of  resistors are these with 5 color bands?

Yeah,  a few things have changed since the good old carbon comp days.

 Check this out:

or this:

There are 4, 5, and 6 banded resistors these days guys! A lot of the resistors I have ordered for the kits are 5 banded. And yeah, some are 4 band so don't let this throw you. If you have to - go ahead and get the old ohmmeter out. No one will ever know!

By the way- most of the resistors are precision metal film 1% tolerance. Where the schematic calls for a 8.2k I may have ordered an 8.25k. That's ok. Go ahead and use it for the 8.2k resistor. Being 1% tolerance it is probably closer to the 8.2k than your old 10% carbon comp resistor would be.

Why did I order the 8.25k anyway? A high precision 8.20k  metal film resistor was not available. The metal film resistors are more stable and less noisy (electrically) than carbon film or carbon composition.