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TI486 Microprocessor - Al Kossow's Bitsavers

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Register Set<br />

Figure 2-1. Application Register Set<br />

31 16 15 8 7 o<br />

--AH ---4x----AL-- EAX<br />

--SH---1fX---- BL<br />

-- EBX<br />

--CH----9- X ----a:-- ECX<br />

- -OH - - - JtX- - - - OL -- EOX<br />

SI<br />

ESI<br />

01 EOI<br />

BP<br />

EBP<br />

SP<br />

ESP<br />

General<br />

Purpose<br />

Registers<br />

15 0<br />

CS<br />

SS<br />

OS<br />

ES<br />

Segment<br />

Registers<br />

FS<br />

GS<br />

31 16 15 0<br />

IP<br />

I EIP<br />

FLAGS<br />

EFLAGS<br />

}<br />

Instruction<br />

Pointer and<br />

Registers<br />

2.3.1.1 General Purpose Registers<br />

The general purpose registers are divided into four data, two pointer registers,<br />

and two index registers as shown in Figure 2-2.<br />

Data Registers<br />

The data registers are used by the applications programmer to manipulate<br />

data structures and to hold the results of logical and arithmetic operations.<br />

Different portions of the general data registers can be addressed by using<br />

different names. An "E" prefix identifies the complete 32-bit register. An "X"<br />

suffix without the "E" prefix identifies the lower 16 bits of the register. The lower<br />

two bytes of the register can be addressed with an "H" suffix to identify the<br />

upper byte or an "L" suffix to identify the lower byte. When a source operand<br />

value specified by an instruction is smaller than the specified destination<br />

register, the upper bytes of the destination register are not affected when the<br />

operand is written to the register.<br />

2-10<br />

Programming Interface

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