Hi Mike,
> I am trying to access a sfr with a pointer (mcs51 P2, P2MDOUT, ...)
It's not a question of the compiler. It is not possible because of the
opcodes of the MCS51. There is no machine instruction to access SFR
through a pointer.
The only solution I once found was to write a function that takes the
address as argument. In the implementation is a huge switch which does
the actual access, like this:
__sfr __at (0x80) SFR_80;
__sfr __at (0x81) SFR_81;
/* ... be hard-working ... */
__sfr __at (0xFF) SFR_FF;
unsigned char readSFR(unsigned char address) {
switch (address) {
case 0x80:
return SFR_80;
case 0x81:
return SFR_81;
/* ... be hard-working ... */
case 0xFF:
return SFR_FF;
default:
return 0; /* or read the internal RAM */
}
}
It's a lot of source code but the object code is quite small. To write
to an arbitrary SFR a similar second function can be written.
HTH
Bodo
------------------------------------------------------------------------------
uberSVN's rich system and user administration capabilities and model
configuration take the hassle out of deploying and managing Subversion and
the tools developers use with it. Learn more about uberSVN and get a free
download at: http://p.sf.net/sfu/wandisco-dev2dev
_______________________________________________
Sdcc-user mailing list
Sdcc-user@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/sdcc-user
