Visible to Intel only — GUID: eis1411613773710
Ixiasoft
Visible to Intel only — GUID: eis1411613773710
Ixiasoft
7.5.1. ALTFP_EXP Design Example: Understanding the Simulation Results
These figures show the expected simulation results in the ModelSim* - Intel® FPGA Edition software.
This design example implements a floating-point exponential for the single-precision format numbers. The optional input ports (clk_en and aclr) and all four exception handling output ports (nan, overflow, underflow, and zero) are enabled.
For single-precision format numbers, the latency is fixed at 17 clock cycles. Therefore, every exponential operation outputs the results 17 clock cycles later.
Time | Event |
---|---|
0 ns, start-up | data[] value: 1A03 568Ch Output value: An undefined value is seen on the result[] port, which is ignored. All values seen on the output port before the 17th clock cycle are merely due to the behavior of the system during start-up and should be disregarded. |
82.5 ns | Output value: 3F80 0000h As the input value of 1A03568Ch is a very small number, it is seen as a value that is approaching zero, and the result approaches 1 (which is represented by 3F800000). Exponential operations carried out on numbers of very small magnitudes result in a 1 and assert the underflow flag. Exception handling ports: underflow asserts |
30 ns | data[] value: F3FC DEFFh This is a normal negative value of a very large magnitude. |
112.5 ns | Output value: 0000 0000h The outcome of exponential operations on negative numbers of very large magnitudes approaches zero. Exception handling ports: underflow remains asserted |
60 ns | data[] value: 7F80 0000h This is a positive infinite value. |
142.5 ns | Output value: 7F80 0000h The operation on positive infinite values results in infinity. Exception handling ports: underflow deasserts, overflow asserts |
90 ns | data[] value: 7FC0 0000h This is a NaN. |
172.5 ns | Output value: 7FC0 0000h The exponential of a NaN results in a NaN. Exception handling ports: nan asserts |
120 ns | data[] value: C1D4 49BAh This is a normal value. |
202.5 ns | Output value: 2C52 5981h The result is a normal value. Exception handling ports: nan deasserts |