I think the best approach is to review the available literature on assembly language coding, and particularly related to the simpler processors. This will give you an idea of the kinds of software systems that are employed; in each case, there will be an executable program that will process your assembly language code to generate machine executable code (something that can be loaded into the main memory of a computer and processed directly by the instruction processor). One example is MASM from Microsoft; it generates code for the x86 series of processors. There is probably another similar product available from Intel Corporation. If you have just a little savvy in programming, then you can write your own assembler.
And, that is an important distinction.
One does not write programs in assembler; indeed, it suggests ignorance of the technology for one to describe the task of writing programs in assembly language by the foregoing phrase. Programming is the task of writing programs, and those who write programs are called programmers.
As a final consideration, do be aware that by judicious use of all available machine facilities, one can obtain dramatic increases in processor throughput; this is a capability generally unavailable to those who write programs in higher level languages, including C, the high-level assembly language.
Above discussion is good, for 32 bit computer, not needed for three chip module. No need to use gun to kill a fly. Take one available 8,16 or 32 bit cheap processor, one RAM chip(which can be replace be EPROM latter when needed), one 8255 I/O. Using buffer. develop your own module, write main program in op code (few line waiting for interrupt) define stack, write needed,small subroutine for your define work(instrumentation, protection or control), generate required signal, for interrupt pin, to be used of your processor, connect it. First check the main program for interrupt by writing out put through 8255.Can use my papers for better understanding. Learn ABCD..., words then go for sentences or grammer
@Peter: You have taken much space to describe how you were able to accomplish various tasks in light of general ignorance of available solutions. Nothing wrong with that; shows fortitude and initiative. Yet, your words above are not particularly inviting; indeed, they come off quite rude.
Try to find The Waite's Group's Microsoft Macro Assembler Bible, by Nabajyoti Barkakati or IBM PC Assembly Language and Programming by Peter Abel. As @Peter Breuer just said above, forget about Integrated Development Environment.