#define SBIT(name, addr, bit) __bit __no_init volatile boolean name @ (addr+bit)
I believe I understand the first part of the above line, "#define SBIT(name, addr, bit)"
But I do not understand the second part, "__bit __no_init volatile boolean name @ (addr+bit)"
What does the second part mean and what does it have to do with the first?
I've never seen a @ operator in C.
I'm guessing it's some non-standard dialect (not Arduino either) way of placing a single bit bool in a particular bit in memory.
Where did you find it?
I think it's a macro to set a bit at the specified address? Or to create a variable that represents a bit at a specific location?
Something like that. I don't think that's Arduino code though - googling the line turned it up only in code for 8051 series microcontrollers. Context suggests that it's for things like setting a single bit in an 8 bit register, which is consistent with my intuition.
Uses directives specific to one compiler I suspect...
IAR Embedded Workbench (Products | IAR) uses that kind of syntax.
__bit: “The __bit memory attribute overrides the default storage of variables given by the selected data model and places individual variables and constants in bit addressable memory. You cannot create a pointer to bit memory.”
__no_init: not initialized at startup
volatile: (standard C/C++) the value can change any time and must be loaded from memory every time it is used
boolean name: type and variable name as usual
@ (addr+bit): variable is located at given address