You can't expect a person lacking in experience to lay out what KEIL charges.

It's not professional work until the people doing the work are capable of working independently on the job. Until they're being paid for it, and nobody having possession of his sense would task someone inexperienced as the O/P clearly indicates he is, to undertake a job such as this as part of a commercial project.

SDCC is just as effective, though perhaps not quite as easy and convenient as KEIL, but not so costly. Until there's a no-cost version of KEIL that can be used to develop code up to 64KB in size, and supporting precise simulation of every available variant, it should be left to those who have more money than good sense.

Another approach, at least for getting started, would be a simple monitor ROM, for example, using ULTRAMON51, which has an internal line-by-line assembler and disassembler, somewhat reminiscent of "debug.exe" under DOS. Paired with a reasonable assembler and simulator, as provided with SDCC, this can bridge the gap between the firmware segments that have to be written in assembler, and debugged in-situ because of hardware constraints, and those that can readily be handled in SDCC's environment.

This sort of work, undertaken by inexperienced participants, must be attacked in small steps. As familiarity with the tools and the MCU architecture increases, the work output will increase as well. Only after the persons working on this project are intimate with both the tools and the MCU architecture will any major investment be warranted.

While it is wise to consider the use of 'C' language, much of the work will have to be done in assembler in order to have precise control of the hardware. Until the participants are intimate with the benefits of assembler over 'C' language should HLL of any sort be used. The benefits of HLL are quite obvious, but it is very important that persons participating in an MCU project don't confuse programming the MCU with programming a PC.

If there's lots of money available, then, OK, go ahead and use KEIL. If you need to develop something meaningful at low cost, or, for that matter, anything at all, SDCC is the tool of choice. After all, a competing MCU manufacturer doesn't own SDCC.

RE