Hi, I want to create a bit field structure for a group of bits associated with 'sfr P1' /* Bit definitions within sfr P1 */ #define NRAMEN (1 << 5) #define A20 (1 << 4) #define A19 (1 << 3) #define A18 (1 << 2) #define A17 (1 << 1) #define A16 (1 << 0) #define NCSDUART NRAMEN+A18 struct myp1 { unsigned char bankSelect :6; /* select banked device */ unsigned char wdog :1; }; struct myp1 data port1 _at_ 0x90; /* problem line doesnt work */ My problem is the last line, how do i get my struct to use P1 so I can do the following ? port1.bankSelect = NCSDUART; /* set/res the appropriate bits on port1 */ Or will i have to start doing something like the following (which i was trying to avoid)? P1 = (P1 & 0xC0) + NCSDUART; /* mask off unwanted bits then select appropriate banked device */ Thanks Mark.
Have you looked at the bit-addressing facilities of C51? Look up "Bit Addressable Objects" in the manual.