gnupic: pre-announcing Forth for PIC18F chips
Subject:
RE: pre-announcing Forth for PIC18F chips
From:
####@####.####
Date:
18 Jan 2005 17:46:09 +0000
Message-Id: <F770B96908E9C64192A137817B8198BD03C9A0@wcosmb06.cos.agilent.com>
Is there any (PIC18) Forth language documents available?
Thank you!
- Mengjin -
-----Original Message-----
From: David McNab ####@####.####
Sent: Sunday, January 16, 2005 6:04 AM
To: ####@####.#### ####@####.####
Subject: pre-announcing Forth for PIC18F chips
Hi gnupic and picforth people,
This is a pre-announcement of a coming Forth compiler for the PIC18Fxxx
chips. I've tentatively called it 'PIC18forth', but am open to
suggestions for a better name.
PIC18forth is radically different from the PIC16Fxxx-only PicForth
compiler. Almost nothing in common, since I've written PIC18forth from
scratch.
Quick summary of features - love them and loathe them:
* signed/unsigned 16-bit data cells and operators
* software return stack
* data stack grows up (increasing addresses), while
return stack grows down (decreasing addresses)
* total allocated size of data+return stacks can
be set to anything between 16 and 1024 bytes
* compiler is written in Python, and is very approachable
and extensible, even for people new to the code
* integrated into gputils
* forth sources get compiled to relocatable assembly (.asm)
sources, ready for gpasm and gplink
* the generated code embeds a 16-bit forth vm (token threaded
execution model) which executes bytecodes
* the generated code is self-contained, and once assembled
and linked, can be downloaded/flashed as a standalone program
* FSR0 is usually used for data stack ptr, FSR1 usually
used as return stack ptr, FSR2 used as general purpose
pointer
* full support for locals (John Hopkins syntax, data
gets transferred from data stack to a frame on return stack
* vm design favours code density over execution speed
* contents of 'code .. end-code' definitions are included
verbatim in generated assembly source (with '\' comments
changed to ';')
* the defining-words 'primitive .. end-primitive' can be
used in place of 'code .. end-code', to define a word
in assembler which will be available as a single-byte
vm instruction - easy to add/remove primitives at will
* maps to von Neumann memory model, with addresses <8000H
treated as RAM addresses, and addresses>=8000H treated
as program ROM addresses
If you're currently hacking with PIC18Fxxx chips, and are interested in
trying out PIC18forth, please mail me and I'll put you on a list for
pre-alpha-testers.
--
Cheers
David
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