The fault can be easily diagnosed in the micro-program control unit using diagnostic tools by maintaining the contents of:
In a micro-program control unit, diagnostic tools help in detecting faults by observing and maintaining important internal states.
These internal states include flags, registers and counters.
Flags store status information, registers store intermediate data and counters help in tracking sequence or control steps.
Therefore, fault diagnosis becomes easier by maintaining the contents of flags, registers and counters.
Consider the following x86 assembly language instructions:
MOV AL, $153$
NEG AL
The contents of the destination register AL in $8$-bit binary notation, the status of Carry Flag $(CF)$ and Sign Flag $(SF)$ after the execution of above instructions, are:
Given,
$AL=153$
Binary form of $153$ is
$10011001$
The instruction NEG AL performs two's complement.
So,
Two's complement of $10011001$ is
$01100111$
Therefore,
$AL=01100111$
Since the operand is non-zero, Carry Flag is set.
So,
$CF=1$
The result $01100111$ has most significant bit $0$.
So, Sign Flag is
$SF=0$
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