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TI486 Microprocessor - Al Kossow's Bitsavers

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Register Set<br />

2.3.1.3 Instruction Pointer Register<br />

2.3.1.4 Flags Register<br />

Figure 2-4. EFLAGS Register<br />

3<br />

1<br />

The Instruction Pointer (EIP) register contains the offset into the current code<br />

segment of the next instruction to be executed. The register is normally<br />

incremented with each instruction execution unless implicitly modified through<br />

an interrupt, exception, or an instruction that changes the sequential execution<br />

flow (e.g., jump, call).<br />

The Flags Register, EFLAGS, contains status information and controls certain<br />

operations on the <strong>TI486</strong> microprocessor. The lower 16 bits of this register are<br />

referred to as the FLAGS register that is used when executing 8086 or 80286<br />

code. The flag bits are shown in Figure 2-4 and defined in Table 2-4.<br />

2 2<br />

4 3<br />

I<br />

0 000 0 0 0 o 0 o 0 0 0<br />

ALIGNMENT CHECK --S ~<br />

VIRTUAL 8086 MODE --S<br />

RESUME FLAG -- D<br />

NESTED TASK FLAG -- S<br />

I/O PRIVILEGE LEVEL --S<br />

OVERFLOW --A<br />

DIRECTION FLAG --C<br />

INTERRUPT ENABLE --S<br />

TRAP FLAG -- D<br />

SIGN FLAG --A<br />

ZERO FLAG --A<br />

AUXILIARY CARRY -- S<br />

PARITY FLAG --A<br />

CARRY FLAG --A<br />

I<br />

FLAGS<br />

I~ ______________ ~A~ ______________ ~\<br />

1111111 1<br />

8765432 o 9 8 7 654 3 2 1 0<br />

A V R 0 N 10 0 D I<br />

C M F T PL F F F<br />

I<br />

T S Z<br />

0 A P C<br />

F F F F<br />

0<br />

F 1<br />

F<br />

A = Arithmetic Flag, D = Debug Flag, S = System Flag, C = Control Flag<br />

o or 1 Indicates Reserved<br />

2-15

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