8086 Special Purpose Registers

Posted By on September 21, 2014


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There are two special purpose registers on the 8086 CPU: the instruction pointer (ip) and the flags register. You do not access these registers the same way you access the other 8086 registers.
Instead, the CPU generally manipulates these registers directly. The ip register is the equivalent of the ip register on the x86 processors ­ it contains the address of the currently executing instruction. This is a 16 bit register which provides a pointer into the current code segment (16 bits lets you select any one of 65,536 different
memory locations). We’ll come back to this register when we discuss the control transfer instructions later.
The flags register is unlike the other registers on the 8086. The other registers hold eight or 16 bit values. The flags register is simply an eclectic collection of one bit values which help determine the current state of the processor. Although the flags register is 16 bits wide, the 8086 uses only nine of those bits. Of these flags, four flags you use all the time: zero, carry, sign, and overflow. 
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Posted by Akash Kurup

Founder and C.E.O, World4Engineers Educationist and Entrepreneur by passion. Orator and blogger by hobby

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