Alu Zero Flag (Az); Alu Underflow Flag (Az, Aus); Alu Negative Flag (An); Alu Overflow Flag (Av, Aos, Avs) - Analog Devices ADSP-2106x SHARC User Manual

2 Computation Units
STKY
Bit Name
0 AUS
1 AVS
2 AOS
5 AIS
Flag update occurs at the end of the cycle in which the status is generated
and is available on the next cycle. If a program writes the ASTAT register
or STKY register explicitly in the same cycle that the ALU is performing
an operation, the explicit write to ASTAT or STKY supersedes any flag
update from the ALU operation.

2.5.3.1 ALU Zero Flag (AZ)

The zero flag is determined for all fixed-point and floating-point ALU
operations. AZ is set whenever the result of an ALU operation is zero.
AZ also signifies floating-point underflow; see the next section. It is
otherwise cleared.

2.5.3.2 ALU Underflow Flag (AZ, AUS)

Underflow is determined for all ALU operations that return a floating-
point result and for floating-point to fixed-point conversion. AUS is set
whenever the result of an ALU operation is smaller than the smallest
number representable in the output format. AZ is set whenever a
floating-point result is smaller than the smallest number representable in
the output format.

2.5.3.3 ALU Negative Flag (AN)

The negative flag is determined for all ALU operations. It is set whenever
the result of an ALU operation is negative. It is otherwise cleared.

2.5.3.4 ALU Overflow Flag (AV, AOS, AVS)

Overflow is determined for all fixed-point and floating-point ALU
operations. For fixed-point results, AV and AOS are set whenever the
XOR of the two most significant bits is a 1; otherwise AV is cleared. For
floating-point results AV and AVS are set whenever the post-rounded
result overflows (unbiased exponent > 127); otherwise AV is cleared.
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Definition
ALU floating-point underflow
ALU floating-point overflow
ALU fixed-point overflow
ALU floating-point invalid operation