Floating-Point IP Cores User Guide

ID 683750
Date 9/13/2021
Document Table of Contents

14.4.1. ALTFP_COMPARE Design Example: Understanding the Simulation Results

The simulation waveform in this design example is not shown in its entirety. Run the design example files in the ModelSim* - Intel® FPGA Edition software to see the complete simulation waveforms.

This figure shows the expected simulation results in the ModelSim* - Intel® FPGA Edition software.

Figure 37. ALTFP_COMPARE Simulation Waveform

This design example implements a floating-point comparator for single-precision numbers. Both optional input ports (clk_en and aclr) and all seven output ports (ageb, aeb, agb, aneb, alb, aleb, and unordered) are enabled.

The chosen output latency is 3. Therefore, the comparison operation generates the output result 3 clock cycles later.

This table lists the inputs and corresponding outputs obtained from the simulation in the waveform.

Table 79.  Summary of Input Values and Corresponding Outputs
Time Event
0 ns, start-up dataa[] value: 619B CE11h

datab[] value: 9106 CA22h

Output value: An undefined value is seen on the result[] port, which is ignored. All values seen on the output port before the 3rd clock cycle are merely due to the behavior of the system during start-up and should be disregarded.

25 ns Output ports: ageb, aneb, and agb assert
350 ns dataa[] value: 0060 0000h

datab[] value: 0070 0000h

Both input values are denormal numbers.

375 ns Output ports: aeb, ageb, and aleb assert

Denormal inputs are not supported and are forced to zero before comparison takes place, which results in the dataa[] value being equal to datab[].

460 ns The aclr signal is set for 1 clock cycle.
495.5 ns The comparisons of subsequent data inputs are performed 3 clock cycles after the aclr signal deasserts.

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