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The following is a partial list of the 8051's registers, which are memory-mapped into the special function register space: Stack pointer, SP (0x81) This is an 8-bit register used by subroutine call and return instructions. The stack grows upward; the SP is incremented before pushing and decremented after popping a value. Data pointer, DP (0x82 ...
The Infineon XC800 family is an 8-bit microcontroller family, first introduced in 2005, [1] with a dual cycle optimized 8051 "E-Warp" [2] [3] core. The XC800 family is divided into two categories, the A-Family for Automotive and the I-Family for Industrial and multi-market applications.
For x86 ALU size of 8 bits, an 8-bit two's complement interpretation, the addition operation 11111111 + 11111111 results in 111111110, Carry_Flag set, Sign_Flag set, and Overflow_Flag clear. If 11111111 represents two's complement signed integer −1 ( ADD al,-1 ), then the interpretation of the result is -2 because Overflow_Flag is clear, and ...
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 ...
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.
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.
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The basic unit of digital storage is a bit, storing a single 0 or 1. Many common instruction set architectures can address more than 8 bits of data at a time. For example, 32-bit x86 processors have 32-bit general-purpose registers and can handle 32-bit (4-byte) data in single instructions. However, data in memory may be of various lengths.