MCU unit, bytes, bits, MCU bit addresses and byte addresses

A byte is 8 binary bits.

89C51 is an 8-bit single-chip microcomputer, so most of the memory units are single-byte (that is, 8 bits), but there are also 16-bit, such as program counter PC and data pointer dptr (in fact, DPTR is composed of two single bytes of DPL and DPH, which can be operated separately, such as MOV DPL, 80h, or directly operated with 16 bits, such as inc dptr and MOV DPTR, 3000h, while PC is 16-bit, and cannot be operated with instructions such as MOV, because it can't be addressed).

The internal RAM of 51 is divided into register area (00h-1fh), bit addressing area (20h-2fh), user area (30h-7fh) and sfr area (special register area, where special registers such as acc, psw, tmod, sp and so on are located), all of which are 8 bits.

With regard to bits, there are no separate bits, any bit is present in a certain byte.

Each byte and bit has its own address, so I won't say much about the address because you didn't ask.

1 byte = 8 bits.

It's like 01010101 is 1 byte.

There are only two states, 1 and 0, for the 1 bit.

51Most of the registers in the microcontroller are 8 bits, which can represent 0-255 and each memory cell is also 8 bits.

In general: 1 memory unit ==1 byte;

Register of 51 ==1 byte;

Of course, some are 16-bit registers ==2 bytes;

Just like the previous masters said.

1 cell = 1 byte = 8 bits.

It can be done on the entire register, or on a single bit with pseudo-instructions.

First question: A byte is 8 bits, so it's 2 8 not 2 10 as you say

The second problem: the address area of 51 single-chip camera is 20h 2fh, and the corresponding bit address is 00h 7fh, and it is a special function register area from 80h, such as p0, the address is 80h, and the corresponding "bit" address of each bit is 80h 87h, so the special function register can only be divisible by 8 addresses to be addressed. The rest of the special function registers are bit-addressable.

A bit is a unit of measurement for the number of binary bits, e.g. 1101b is 4 bits; 1 byte (1 byte) = 8 bits; The landlord's "8 bits are 256 bytes" is difficult to understand, and the original meaning should be that 8 is a binary number that can represent 256 different binary numbers 00000000b 11111111b

Isn't it possible to calculate according to the number of times of 2, 2 to the 8th power of 256, and so on.

First of all, what you said is not right. 8 bits are not 256 bytes, and 16 bits are not 65536 bytes.

The correct one is this: a byte has 8 bits of binary bits. This is true not only in microcontrollers, but also in computers as a whole, even in digital circuits.

The 8 bits can represent 256 states, and each binary has two states, 0 and 1, and the 8 bits are the 8th power states of 2.

These 256 states can represent 256 unsigned integers such as 0 255, 256 signed integers from 128 to +127, and decimals, etc., and these representations are called data types.

Programming mnemonics cannot speak bytes, but bytes are the length of instructions. Strictly speaking, its length has nothing to do with the machine cycle. Because the machine cycle is the number of machine cycles consumed by the specified execution, it is related to read, write memory, and operational complexity, such as the multiplication operation of an 8-bit machine, the instruction is not long, but it itself is calculated as an addition method, which consumes a lot of machine cycles.

In ARM microcontrollers, the instruction length of fetching data and storing data is naturally fixed, but the storage cycle consumed varies with the amount of data.

The 16 byte units of the single-chip microcomputer from 20h to 2fh, a total of 128 bits can be addressed by bit, corresponding to the bit addressing space from 00h to 7fh, so the unit address with a bit address of 40h is 40h 8+20h=28h.

In addition, there are 16 special function registers that can be addressed, just check ** on the line, 88h corresponding to the byte address is also 88h. In the same way, 2ah-20h=0ah, 0ah*8=50h.

The 20H 2FH of the RAM on the chip of the single-chip microcomputer, which is 16 bytes, can be addressed according to the "bits" of the precautionary light.

There are a total of 128 "bit addresses", which are 00h and 7fh.

For example, the bit address 4EH is the 6th bit of the "byte unit with a byte address of 29h".