Search results
Results from the WOW.Com Content Network
[3] [49] 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 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 ...
The 8-bit f field determines the address in combination with the a bit and the 4-bit bank select register (BSR). If a =0, the BSR is ignored and the f field is sign-extended to the range 0x000–0x07F (global RAM) or 0xF80–0xFFF (special function registers).
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.
The default OperandSize and AddressSize to use for each instruction is given by the D bit of the segment descriptor of the current code segment - D=0 makes both 16-bit, D=1 makes both 32-bit. Additionally, they can be overridden on a per-instruction basis with two new instruction prefixes that were introduced in the 80386:
s is a bit number in the status register (0 = C, 1 = Z, etc., see the list above) b is a bit number in a general-purpose or I/O register (0 = least significant, 7 = most significant) K6 is a 6-bit immediate unsigned constant (range: 0–63) K8 is an 8-bit immediate constant; since it is used only in 8-bit operations, its signedness is irrelevant
Computer architectures are often described as n-bit architectures. In the first 3 ⁄ 4 of the 20th century, n is often 12, 18, 24, 30, 36, 48 or 60.In the last 1 ⁄ 3 of the 20th century, n is often 8, 16, or 32, and in the 21st century, n is often 16, 32 or 64, but other sizes have been used (including 6, 39, 128).
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.