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Construct signed fixed-point numeric object
a = sfi
a = sfi(v)
a = sfi(v,w)
a = sfi(v,w,f)
a = sfi(v,w,slope,bias)
a = sfi(v,w,slopeadjustmentfactor,fixedexponent,bias)
You can use the sfi constructor function in the following ways:
a = sfi is the default constructor and returns a signed fi object with no value, 16-bit word length, and 15-bit fraction length.
a = sfi(v) returns a signed fixed-point object with value v, 16-bit word length, and best-precision fraction length.
a = sfi(v,w) returns a signed fixed-point object with value v, word length w, and best-precision fraction length.
a = sfi(v,w,f) returns a signed fixed-point object with value v, word length w, and fraction length f.
a = sfi(v,w,slope,bias) returns a signed fixed-point object with value v, word length w, slope, and bias.
a = sfi(v,w,slopeadjustmentfactor,fixedexponent,bias) returns a signed fixed-point object with value v, word length w, slopeadjustmentfactor, fixedexponent, and bias.
fi objects created by the sfi constructor function have the following general types of properties:
These properties are described in detail in fi Object Properties in the Properties Reference.
The data properties of a fi object are always writable.
bin — Stored integer value of a fi object in binary
data — Numerical real-world value of a fi object
dec — Stored integer value of a fi object in decimal
double — Real-world value of a fi object, stored as a MATLAB^{®} double
hex — Stored integer value of a fi object in hexadecimal
int — Stored integer value of a fi object, stored in a built-in MATLAB integer data type. You can also use int8, int16, int32, int64, uint8, uint16, uint32, and uint64 to get the stored integer value of a fi object in these formats
oct — Stored integer value of a fi object in octal
These properties are described in detail in fi Object Properties.
When you create a fi object with the sfi constructor function, that fi object does not have a local fimath object. You can attach a fimath object to that fi object if you do not want to use the default fimath settings. For more information, see fimath Object Construction in the Fixed-Point Designer™ documentation.
fimath — fixed-point math object
The following fimath properties are always writable and, by transitivity, are also properties of a fi object.
CastBeforeSum — Whether both operands are cast to the sum data type before addition
OverflowAction — Action to take on overflow
ProductBias — Bias of the product data type
ProductFixedExponent — Fixed exponent of the product data type
ProductFractionLength — Fraction length, in bits, of the product data type
ProductMode — Defines how the product data type is determined
ProductSlope — Slope of the product data type
ProductSlopeAdjustmentFactor — Slope adjustment factor of the product data type
ProductWordLength — Word length, in bits, of the product data type
RoundingMethod — Rounding method
SumBias — Bias of the sum data type
SumFixedExponent — Fixed exponent of the sum data type
SumFractionLength — Fraction length, in bits, of the sum data type
SumMode — Defines how the sum data type is determined
SumSlope — Slope of the sum data type
SumSlopeAdjustmentFactor — Slope adjustment factor of the sum data type
SumWordLength — The word length, in bits, of the sum data type
These properties are described in detail in fimath Object Properties.
When you create a fi object, a numerictype object is also automatically created as a property of the fi object.
numerictype — Object containing all the data type information of a fi object, Simulink^{®} signal or model parameter
The following numerictype properties are, by transitivity, also properties of a fi object. The properties of the numerictype object become read only after you create the fi object. However, you can create a copy of a fi object with new values specified for the numerictype properties.
Bias — Bias of a fi object
DataType — Data type category associated with a fi object
DataTypeMode — Data type and scaling mode of a fi object
FixedExponent — Fixed-point exponent associated with a fi object
SlopeAdjustmentFactor — Slope adjustment associated with a fi object
FractionLength — Fraction length of the stored integer value of a fi object in bits
Scaling — Fixed-point scaling mode of a fi object
Signed — Whether a fi object is signed or unsigned
Signedness — Whether a fi object is signed or unsigned
Slope — Slope associated with a fi object
WordLength — Word length of the stored integer value of a fi object in bits
For further details on these properties, see numerictype Object Properties.
Note For information about the display format of fi objects, refer to Display Settings. For examples of casting, see Cast fi Objects. |
For example, the following creates a signed fi object with a value of pi, a word length of 8 bits, and a fraction length of 3 bits:
a = sfi(pi,8,3) a = 3.1250 DataTypeMode: Fixed-point: binary point scaling Signedness: Signed WordLength: 8 FractionLength: 3
Default fimath properties are associated with a. When a fi object does not have a local fimath object, no fimath object properties are displayed in its output. To determine whether a fi object has a local fimath object, use the isfimathlocal function.
isfimathlocal(a) ans = 0
A returned value of 0 means the fi object does not have a local fimath object. When the isfimathlocal function returns a 1, the fi object has a local fimath object.
The value v can also be an array:
a = sfi((magic(3)/10),16,12) a = 0.8000 0.1001 0.6001 0.3000 0.5000 0.7000 0.3999 0.8999 0.2000 DataTypeMode: Fixed-point: binary point scaling Signedness: Signed WordLength: 16 FractionLength: 12
If you omit the argument f, it is set automatically to the best precision possible:
a = sfi(pi,8) a = 3.1563 DataTypeMode: Fixed-point: binary point scaling Signedness: Signed WordLength: 8 FractionLength: 5
If you omit w and f, they are set automatically to 16 bits and the best precision possible, respectively:
a = sfi(pi) a = 3.1416 DataTypeMode: Fixed-point: binary point scaling Signedness: Signed WordLength: 16 FractionLength: 13
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