3. FixedPoint IP Cores Parameters and Signals
Parameter  Description 

Goal  Select Frequency, Latency, or Combined performance target 
Target  Enter the frequency in MHz at which you expect this function to run. The IP core determines the amount of pipelining from this frequency and the target device family. 
Check Performance  Click Check Performance to view the resource usage. 
Parallel Add
This IP calculates the sum of the inputs.
Turn on Wide adder architecture (under the Options tab) for an architecture optimized for very wide bitwidths. This architecture reduces both resource utilization and latency. The wide adder architecture requires that all inputs share the same format.
Parameter  Description 

Input data widths  
Input name  Autogenerated name of this input to the generated IP core. 
Width  The width of this fixedpoint data interface. 
Fraction  The number of fraction bits in this fixedpoint data interface. 
Sign  The signedness of this fixedpoint data interface. 
+  Click + to add more inputs; click  to remove inputs. 
Output data widths  
Automatic output type  Tturn on automatic output type to allow the IP core to determine the output format based on the input and operation. 
Width  
Fraction  
Sign  
Options  
Disable adder word growth  The addition and or subtraction logic in the IP core normally allows for word growth. To disable word growth turn on this option. 
Generate an enable port  Turn on if you want the function to have an enable signal. 
Wide adder architecture  Turn on for wide operand bitwidths (hundred to thousands of bits) when all inputs share the same formats. 
Wide adder ripplecarry chunk size  This option allows you to set the maximum primitive adder size that the wide adder architecture uses. Intel recommends to set this value to be a multiple of the LAB ripplecarry adder chain size: 20, 40, 60 etc. A value of 40 typically provides a good balance between resource utilization and performance. Specify a value of 20 if you require a very high frequency. 
Signal  Direction  Description 

clk  Input  Clock. 
reset  Input  Reset. 
a0  Input  Input a0. 
a1  Input  Input a1. 
result  Output  The parallel add result. 
Multiply
This IP multiplies the two inputs. The IP provides architectures optimized for multiplying wide operands (tens to thousands of bits), if you turn on Wide multiplier architecture under the Options tab.
Parameter  Description 

Complex Data  You can configure a multiplier to operate on complex valued inputs and optionally use the Karatsuba method for multiplication of complex numbers. Complex valued inputs and outputs are concatenated real and imaginary values of the data format you specify. The real part occupies the lower bits of the input or output bus. Complex multiplication requires four multiplications and two additions. 
Karatsuba complex multiplicaiton  The Karatsuba option reduces the number of multipliers to three, increases the number of adders to five. 
Input data widths  
Width  The width of this fixedpoint data interface 
Fraction  The number of fraction bits in this fixedpoint data interface 
Sign  The signedness of this fixedpoint data interface 
Output data widths  
Automatic output type  Turn on automatic output type to allow the IP core to determine the output format based on the input and operation. 
Width  
Fraction  
Sign  
Options  
Generate an enable port  Turn on if you want the function to have an enable signal. 
Wide multiplier architecture  Use when multiplying wide unsigned operands having the same widths. Allows you to telect the wide multiplier architecture for IP including the classical schoolbook algorithm and several variations of the Karatsuba algorithm. 
Architecture  This dropdown list allows selecting one of four advanced architecture options:

FlatKaratsuba threshold value  This advanced option is available for Hybrid Karatsuba. The threshold value indicates that all multipliers resulting from the recursive Karatsuba decomposition that have sizes smaller or equal to this value are implemented using Flat Karatsuba. Ideal values for this field include multiples of 26 (one less than the DSP Block multiplier size in 27x27 configuration). Select the value of 130 when implementing multipliers of sizes 256, 512, 1,024, 2,048 etc. 
If the IP core cannot represent the product of the inputs in the output format you chose, the result is undefined.
Signal  Direction  Description 

clk  Input  Clock. 
reset  Input  Reset. 
a  Input  Input a. 
b  Input  Input b. 
result  Output  The multiply result. 
Modular Multiply
This IP implements a modular multiplier using Barrett’s algorithm. The IP inputs A, B and the modulus M and returns AB % M. A, B and M share the same bitwidth and they are unsigned. For each set of inputs A, B and M, the IP also requires you to provide R, which is an approximation to the reciprocal of M. R is to be provided on width+1 bits and is computed as R=saturate(floor(4^width/M)). The IP requires that M is in the interval [2^(width1), (2^width)1], and therefore requires that the most significant bit of M is 1.
The IP also allows you to instantiate this modular multiplier for a fixed modulus value. You can input the modulus value using the provided text field. You can select the base used for expressing the modulus value. The modulus value must also be in the interval [2^(width1), (2^width)1].
For example, when width=8 the allowed modulus values are [128, 255].
Parameter  Description 

Width  Width of multiplier inputs A and B, the modulus M and the result. The reciprocal of the modulus R is one bit wider. 
Constant Modulus  Turn on to fix the value of the modulus. 
Modulus Value  Setting the value of the modulus when you turn on Constant Modulus. The modulus value must be in the interval [2^(width1), 2^(width)1]. 
Base  Available when you turn on Constant Modulus. The value in Modulus Value is interpreted in the base indicated by this selection. The four bases are: binary, octal, decimal, and hexadecimal. For example, a modulus value of 1000 and a base of binary corresponds to the decimal value 8. 
Divide
This IP core produces the result of the first input, numerator, divided by the second input, denominator. The Divide IP core has a fixedpoint output. You can control the number of significant bits in the output by adjusting the output data format. If you reduce the number of bits in the output, the divider uses fewer resources.
The LSB in the divider's output is faithfully rounded. Use the Integer Divide IP core to obtain true equivalence to a truncating CPU integer divider. The faithfully rounded result has an accuracy of one unit in the last place, where one unit in the last place is the weight of the LSB. For example, if the output format has zero fraction bits, the weight of the LSB is 2^0=1. If the result is 3.2, the IP core can either return 3 or 4, where both results are equally valid.
Parameter  Description 

Input data widths  
Width  The width of this fixedpoint data interface 
Fraction  The number of fraction bits in this fixedpoint data interface. Divide IP core only. 
Sign  The signedness of this fixedpoint data interface 
Output data widths  
Automatic output type  Turn on to allow the IP core to determine the output format based on the input and operation. 
Width  The width of this fixedpoint data interface. 
Fraction  The number of fraction bits in this fixedpoint data interface. Divide IP core only. 
Options  
Generate an enable port  Turn on if you want the function to have an enable signal. 
Signal  Direction  Description 

clk  Input  Clock. 
reset  Input  Reset. 
numerator  Input  Numerator. 
denominator  Input  Denominator. 
result  Output  The division result. 
Square Root
The output is faithfully rounded. The faithfully rounded result has an accuracy of one unit in the last place, where one unit in the last place is the weight of the LSB. For example, if the output format has zero fraction bits, the weight of the LSB is 2^0=1. If the result is 3.2, the IP core can either return 3 or 4, where both results are equally valid.
Parameter  Description 

Input data widths  
Width  The width of this fixedpoint data interface 
Fraction  The number of fraction bits in this fixedpoint data interface 
Sign  The signedness of this fixedpoint data interface 
Output data widths  
Automatic output type  Turn on to allow the IP core to determine the output format based on the input and operation. 
Width  The width of this fixedpoint data interface. 
Fraction  The number of fraction bits in this fixedpoint data interface. 
Sign  The signedness of this fixedpoint data interface. 
Options  
Generate an enable port  Turn on if you want the function to have an enable signal. 
Signal  Direction  Description 

clk  Input  Clock. 
reset  Input  Reset. 
radical  Input  — 
result  Output  The square root result. 
Integer Divide
This IP core produces the result of the first input, numerator, divided by the second input, denominator. The Divide IP core has a fixedpoint output. You can control the number of significant bits in the output by adjusting the output data format. If you reduce the number of bits in the output, the divider uses fewer resources.
The Integer Divide IP core offers true equivalence to a truncating CPU integer divider.
Parameter  Description 

Input data widths  
Width  The width of this fixedpoint data interface 
Sign  The signedness of this fixedpoint data interface 
Output data widths  
Automatic output type  Turn on to allow the IP core to determine the output format based on the input and operation. 
Width  The width of this fixedpoint data interface. 
Options  
Generate an enable port  Turn on if you want the function to have an enable signal. 
Signal  Direction  Description 

clk  Input  Clock. 
reset  Input  Reset. 
numerator  Input  Numerator. 
denominator  Input  Denominator. 
result  Output  The division result. 
Simple Counter
This IP core maintains a counter and produces the counter value each cycle.The value of the counter increments by the positive step value every cycle for which the enable input is high.
The counter limit is its rollover value. The IP core sizes a counter to accommodate a value one less than the limit you specify. For example, a limit of 65,536 specifies a 16bit counter. If the start value is 0 and the step value is 1, the counter rolls over from 65,535 to 0.
The limit must be equal to start plus an integer multiple of step.
Parameter  Description 

Start value  The counter initialises to this value on reset and when incrementing a step reaches the Limit. The Start value must be greater than zero. 
Step  The increment that the IP core applies on each cycle when the counter's enable input is high. The simple counter's step must be positive. Step must be greater than zero. 
Limit  The counter counts up to one step away from this value. If adding the step value to the counter reaches the limit, the counter returns to Start value. Limit must be greater than or equal to Start. 
Signal  Direction  Description 

clk  Input  Clock. 
rst  Input  Reset. 
en  Input  Enable. 
value  Output  — 
Loadable Counter
This IP core maintains a counter and produces the counter value each cycle.T
You configure the counter with start value, step and limit values. You specify an initial configuration at setup time using the IP GUI. The counter always uses this configuration on reset. The counter allows changing configurations at runtime. To set new values at runtime, change the corresponding input signals (start, step and limit) and hold the sload signal high for one cycle.
The initial reset initializes the counter to the setup start value. Then counter value gets incremented by the step value in every cycle for which the enable signal is high.
You can specify the counter width and its sign. These values determine the range of the counter [minValue, maxValue]. If the counter type is wbit unsigned, minValue=0 and maxValue=(2^width) – 1. If the counter type is wbit signed, minValue=2^(width1) and maxValue=(2^(width1))1.
For positive limit values, and when enable is high, the next value of the counter is computed as (value + step) % limit. % denotes the remainder operation.
For example, for a 5bit signed counter, which is loaded with start value=7, step=3 and limit=13, the counter values are 10, 0, 3, 6, 9, 12, 2, 5, 8.
When the limit is negative, the next counter value is minValue + ((value + step) % (maxValue+1)). As the next counter value exceeds the set limit, the next counter value is computed as the difference between this value and the limit.
For example, for a 5bit signed counter, which is loaded with start value=13, step=3 and limit=10 the next counter value is 16 + ((13+3)%16) = 16. The value after that is 16+3=13. The next value 13+3=10 reaches the limit, and the next counter value is set to 10(10)=0. The next values are 3, 6, 9, 12, 15. The next counter value after 15 is (16 + ((15+3)%16))=14. The value after is 11. The next value is (11+3)(10)=2.
The loadable counter requires that step is a positive value. The IP requires the initial start value and limit are also positive values, and that their difference be a multiple of the step size.
Parameter  Description 

Start value  The counter initializes to this value on reset and when incrementing a step reaches the Limit. 
Step  The increment that the IP core applies on each cycle when the counter's enable input is high. 
Limit  The counter counts up to one step away from this value. If adding the step value to the counter reaches the limit, the counter returns to Start value. 
Output data widths  
Width  The width of this fixedpoint data interface. The width of the counter and its Start, Step, and Limit inputs. 
Sign  The signedness of this fixedpoint data interface. Although the interface may be signed, the IP only supports the unsigned range of values for start and step. 
Signal  Direction  Description 

clk  Input  Clock. 
rst  Input  Reset. 
en  Input  Enable. 
sload  Input  When sload is high, the IP replaces the counter's internal start, step, and limit values by values from the corresponding input signals. The counter requires that you provide positive values for start and step. 
step  Input  
start  Input  
limit  Input  
value  Output 
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