What are bit and sbit in 51 MCU? _ Difference between bit and sbit-EEWORLD

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Looking back at the C language, I found that there are some types such as bit sbit sfr in the microcontroller!

Question: What are bit and sbit? What is the difference between them?

　　bit : space allocated at compile time

sbit can only be defined externally as a global variable.

The bits of sfr (special function register). SFR is the memory address specified by the system.

　　bit is dynamically allocated, and the compiler specifies the memory address.

　　Both bit and sbit are variable types extended by C51.

　　sbit must be defined at the outermost position, that is, it must be defined as an external variable. sbit defines the bit of SFR (special function register)

　　sbit is more like a type definition than a variable definition.

　　sbit: indicates descriptive instructions

　　A bit can be defined externally or internally.

　　Bit is similar to int char, except that char = 8 bits, bit = "1 bit". They are all variables, and the compiler assigns addresses during the compilation process. Unless you specify it, the address is random. This address is the entire addressable space, RAM + FLASH + expansion space. Bit has only two values 0 and 1, and its meaning is a bit like BOOL in VC under Windows.

　　bit is a bit variable allocated by the compiler in the addressable area. It is indefinite and not an absolute address target.

　　All bit-addressable bits can be specified by sbit, including bits in bit-addressable areas and SFRs.

　　sbit is a bit in the addressable space, which is from 20H to 2FH. Once the definition sbi xxx = REGE^6 is used, the sbit value determines the address. Most sbits are used in registers to facilitate operations on a certain bit of the register.

　　The sbit register is a bit-addressable absolute address target, and the compiler will not change the position after definition.

I hope the above summary will be helpful to beginners.

Reference address：What are bit and sbit in 51 MCU? _ Difference between bit and sbit

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