On 2/08/2013 6:58 PM, Philipp Klaus Krause wrote:

> To decide if sdcc would be a good option more information is necessary. Is
> there any public information on the architecture of this custom processor?
Unfortunately, no. In fact, I know very little about it myself right now, 
other than a brief listing of the instruction set opcodes and some ALU details.

To give some background; a professional contact is developing a custom 
soft-core processor with the aim of providing it to customers (presumably at 
a price) requiring a processor in very small FPGA's. He has a table-driven 
assembler written by a friend that he is using to develop/test the core, and 
is currently implementing interrupts. He has asked me (yesterday) if I'd be 
interested in developing the C compiler/toolchain for it. Details atm are 
scant but I've started researching as far as possible and thus far SDCC is 
looking like an ideal candidate.

> Of course you also need an assembler and linker, but you would with any
> compiler.

On that note; I'm assuming that I could write a GAS-compliant assembler for 
SDCC - yes?

> Also, this is isn't just a matter of putting so-and-so much time into a
> port and then it is there. Sure there is a point at which most of the
> regression tests pass, and the port can be merged into trunk. But there
> are always bugy to fix, and there is potential for optimization. I
> consider the stm8 port an ongoing effort (as any other port).

Noted, and well understood. I'm currently writing a 6309 core in VHDL myself...

> I started working on it at the beginning of this year. No one really
> worked on the port full-time. Valentin mostly worked on the assembler and
> linker on weekends. You might want to have a look at the number of lines
> in src/stm8/gen.c and estimate the effort from there (the other big files
> in src/stm8 are mostly just copied from other ports with a few small
> modifications). Philipp

Have subsequently done so, and many thanks for the advice! I'm starting to 
get a feel for what's required now. I'm particularly intimate with the Z80 
as well, so that might be a good reference for me as well as the STM8, which 
looks decidedly simpler than the Z80 looking at the STM8 CPU Programming 
Manual! ;)

I'm leaning heavily towards SDCC atm, especially if I can assume that any 
work I do on assembler/linker - which I'd start with - would be equally 
valid for any front-end. If nothing else, it'd be a fun learning exercise 
anyway!

Regards,
Mark


-- 
Mark McDougall, Engineer
Virtual Logic Pty Ltd, <http://www.vl.com.au>
21-25 King St, Rockdale, 2216
Ph: +612-9599-3255 Fax: +612-9599-3266

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