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Some CPUs [20] permit the 8-bit indirect address to use any 8-bit general-purpose register. To permit the use of this feature, some 8051-compatible microcontrollers with internal RAM larger than 256 bytes, or an inability to access external RAM, [ 20 ] access internal RAM as if it were external and have a special function register (e.g. PDATA ...
Thus numbers ranging from −127 10 to +127 10 can be represented once the sign bit (the eighth bit) is added. For example, −43 10 encoded in an eight-bit byte is 10101011 while 43 10 is 00101011. Using sign–magnitude representation has multiple consequences which makes them more intricate to implement: [5]
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.
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.
This table illustrates an example of an 8 bit signed decimal value using the two's complement method. The MSb most significant bit has a negative weight in signed integers, in this case -2 7 = -128. The other bits have positive weights. The lsb (least significant bit) has weight 2 0 =1. The signed value is in this case -128+2 = -126.
An eight-bit processor like the Intel 8008 addresses eight bits, but as this is the full width of the accumulator and other registers, this could be considered either byte-addressable or word-addressable. 32-bit x86 processors, which address memory in 8-bit units but have 32-bit general-purpose registers and can operate on 32-bit items with a ...
2× 16-bit timers. 12-bit 1 Msps ADC. 12-bit 500 ksps DAC. Zilog eZ80: Fast Z80: 8/16 Production 50: 256: 16 $7.79: 1: 1: 1: 0: 0: 0: 0: Linear addressing up to 16 MB. 3–4× faster than traditional Z80. Texas Instruments MSP430FR2632 RISC 16 16 8 2 $0.924: 126 μA/MHz <5 μA 2 1 1 0 0 8 0
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.