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The Auxiliary Carry flag is set (to 1) if during an "add" operation there is a carry from the low nibble (lowest four bits) to the high nibble (upper four bits), or a borrow from the high nibble to the low nibble, in the low-order 8-bit portion, during a subtraction. Otherwise, if no such carry or borrow occurs, the flag is cleared or "reset ...
[3] [48] It can perform as an 8-bit 8051, has 24-bit linear addressing, an 8-bit ALU, 8-bit instructions, 16-bit instructions, a limited set of 32-bit instructions, 16 8-bit registers, 16 16-bit registers (8 16-bit registers which do not share space with any 8-bit registers, and 8 16-bit registers which contain 2 8-bit registers per 16-bit ...
The result should be 510 which is the 9-bit value 111111110 in binary. The 8 least significant bits always stored in the register would be 11111110 binary (254 decimal) but since there is carry out of bit 7 (the eight bit), the carry is set, indicating that the result needs 9 bits. The valid 9-bit result is the concatenation of the carry flag ...
An 8-bit register can store 2 8 different values. The range of integer values that can be stored in 8 bits depends on the integer representation used. With the two most common representations, the range is 0 through 255 (2 8 − 1) for representation as an binary number, and −128 (−1 × 2 7) through 127 (2 7 − 1) for representation as two's complement.
When the bit numbering starts at zero for the least significant bit (LSb) the numbering scheme is called LSb 0. [1] This bit numbering method has the advantage that for any unsigned number the value of the number can be calculated by using exponentiation with the bit number and a base of 2. [2] The value of an unsigned binary integer is therefore
In computer programming, a bitwise operation operates on a bit string, a bit array or a binary numeral (considered as a bit string) at the level of its individual bits.It is a fast and simple action, basic to the higher-level arithmetic operations and directly supported by the processor.
However, a binary number system with base −2 is also possible. The rightmost bit represents (−2) 0 = +1, the next bit represents (−2) 1 = −2, the next bit (−2) 2 = +4 and so on, with alternating sign. The numbers that can be represented with four bits are shown in the comparison table below.
An example, suppose we add 127 and 127 using 8-bit registers. 127+127 is 254, but using 8-bit arithmetic the result would be 1111 1110 binary, which is the two's complement encoding of −2, a negative number. A negative sum of positive operands (or vice versa) is an overflow.