Me and my developers are developing the code for a tech startup that I have an equity with. I'm giving the code to the startup for the startup purpose use. However, since I'm the developer, I would like to be able to reuse the code or parts of it (not the idea itself) for other ventures.
Is that the default situation or I need specifically mention it in the contract agreement?
To answer your specific query "Is that the default situation..."; in the United States the creator retains the rights to the work by default unless he specifically assigns them. Your software is just like a painter who paints a picture. When someone buys a print of the picture that is all they get, they do not get any rights to the original and can not produce and sell other prints etc.
Thant having been said, the most ethical thing to do is to fully disclose in a written agreement exactly what rights you are giving to the startup and what you intend to retain. This can prevent misunderstandings and disputes down the road.
In the US, software is owned by the developer unless they specifically assign their rights away. This is true even if company A paid Contractor B to develop the software! The software is property of Contractor B. For employees too this holds true but most employment agreements already have the assignment clause, so nobody looks at this later on each project.
A quick google search yielded : http://www.bitlaw.com/copyright/license.html - check it out.
Once you assign the rights to another entity (eg. other company), you lose those rights. And usually all rights are assigned so company A can state "Blah blah. Copyright 2012. All rights reserved".
I'm not a lawyer but I suspect you could assign all rights to the other company and in the same paragraph have the company license the software back to you for your non-competitive purposes. It can be tricky because it's likely the "non-idea specific" code is generic enough that the company would like to reuse that investment in it's future - without ANY worries that it find you competing against them in that new sector with the exact same code! It really depends what's acceptable to you and the other company. If you guys agree then pick a lawyer to draft the agreement. Minimizing the lawyer involved customizations to just this one thing in an otherwise generic agreement should keep your costs ~$200-$400 region.
I feel instead of transferring the complete code, you can give the LLC right to use or License to Use the software. A token royalty amount can be prescribed. Your agreement should make it explicit that you continue to own the software and the right to use with or without modification at other places as well.