NOTES file for SDCC pic16 port
$Id$

Current pic16 port status is: Development

Some things may change without notification between port updates. The latest
CVS snapshot is guarenteed to compile without problems, but does not
guarantee backwards compatibility.

For any questions please ask the current port
developers.

Current developer:
Vangelis Rokas	<vrokas AT otenet.gr>

Other people to contact:
Scott Dattalo	<scott AT dattalo.com>

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2004-May-23 Vangelis Rokas

1. The improvement of the port has been stalled a bit. But, struct/union
SFR headers are ready for the PIC18F[45][45][28] chips along with their
respective sources.

2. The genCmp function should be rewritten from scratch.

3. The internal helper functions for char/int/long/float arithmetic
now compile and will be placed in the appropriate directory under device/



2004-Feb-20 Vangelis Rokas
Major update with many bugfixes.

1. The most of the pic16 regression tests (former pic regression tests) pass
successfully. Many thanks to Hans Dorn who did a great job with the
arithmetic, shift and pointer functions.

2. Bit fields now work properly.

3. Stack is permanently enabled. Command argument -pstack-enable is deleted
and no more recognized by the port.


2004-Feb-07 Vangelis Rokas

1. Fixed a bug so that compiler allocated internal registered, will
be shared along multiple sources via '.registers' section placed
in absolute data memory address 0x0000. Registers 0x00 to 0x7f are
considered as internal since they can be used for fast access.



2004-Jan-11 Vangelis Rokas

1. Compiling
The current release of the port can produce object code which is not
completely bug free. To use the new features the user should enable them via
command line arguments. A sane set of command arguments that I use to test
programs is:

- debug options
	--debug		enable sdcc debug information
	--debug-xtra	enable pic16 port debug information (most useful)
	--debug-ralloc	enable register allocator debug messages
	--pcode-verbose	enable verbose pcode generator messages

- port options
	--pgen-banksel	enable banksel directives for the assembler
			This will be turned on by default later, but left as
			is for now
	--pomit-config-words	does not emit configuration instruction in
			the translation This is useful when copmiling
			multiple sources, when you do not want multiple
			config instructions in the end file
	--pomit-ivt	disables the dumping of the interrupt vector tables
			in the translation for the same reasons as above
	--penable-stack	enables stack support. This option uses stack to
			pass function arguments, and reuses registers between
			functions by saving the registers used in the function
			on the stack

- compiler options
	--all-callee-saves	you may omit this options as the port
			enables it by default, all functions are currently
			compiled as reentrant and they are marked as
			callee-saves
	--no-peep	peephole optimizer is better to be switched off,
			because it behaves strangely in some cases
	--fommit-frame-pointer	this omits frame pointer in functions that
			don't use registers (maybe changed later, not
			important)


2. Functions
The current implementation puts every function in its own code section in
PIC's program memory. This may not be the standard, but I think its more
flexible.

3. Pragmas
Since SDCC is goind for a release, its better to document pragmas available.

3.1. code
The 'code' pragma emits a function's code at a specific address in program
memory. Currently it is only used for functions.
Syntax:
#pragma code [function_name] [address]

3.2. stack
The 'stack' pragma initializes the stack/frame pointer at an address of the
data ram other than the default (which is the end of the available data ram)
Synatx:
#pragma stack [address]

3.3. maxram
The 'maxram' pragma sets maximum data ram of the device. Currently is not
used at all, but it may be useful in the future when devices with external
memory will be supported.
Syntax:
#pragma maxram [max_address]


4. Internal compiler functions
Internal SDCC functions like, __fsmul, etc... are currently supported by the
port, but the libraries for the pic16 port are not yet ready. So one cannot
use long and float variables.


5. Special Function Registers (SFRs)
The processor SFRs are not anymore declared in any header file. The user can
define by himself all the needed SFR's. The code to that is:

sfr at [sfr_address] [sfr_name];

Where sfr_address is the SFR address in the data ram, and sfr_name is the
name of the SFR. i.e.:

sfr at 0xf80 PORTA;