Re: [Mspgcc-users] sfrw macro

[Mathias Gruber]

Sergey A. Borshch escreveu: Anthony L wrote: Hi All, Could someone please tell me what the purpose of the sfrw macro is? For example; #define TA0CTL_ 0x0160 sfrw (TA0CTL,TA0CTL_); What would be the difference to defining TA0CTL directly to 0x0160 ? Because #define TA0CTL 0x0160 absolutely useless in C sources. Expanding TA0CTL = 0; to 0x0160 = 0; is meanless. sfrw() macro expanded differently when header file included into C or asm source files. I can't say why sfrw (TA0CTL, 0x0160) notation not used. Possibly we can change headers to this notation to preserve global namespace from flooding with TA0CTL_-like useless names. The C-compliant syntax, to turn the 0x0160 constant into an absolute address would be something like this:     #define TA0CTL ((volatile uint16_t *)(0x0160)) Note that the "volatile" keyword is a MUST, since hardware may change register contents anytime. The sfr notation comes from the Harward architecture, specially the 80x51, where the standard C notation can't cope with some processor specific features, like bit-addressing and other stuff. For modern microcontrollers such as ARM and MSP430 this is really an optional compiler extension.