Intel Floating Point FFT IP Gives Different Result to Python Example

To expand upon this issue, I have made a simpler test case which I will now describe. I am still trying to calculate an IFFT.

The input to the FFT IP core is the following array:

[(1+1j), (1+1j), (1+1j), (1+1j), (1+1j), (1+1j), (1+1j), (1+1j), (1+1j), (1+1j), (1+1j), (1+1j), (1+1j), (1+1j), (1+1j), (1+1j)]

A really simple sequence of 16 "ones".

The expected IFFT is:

[1.+1.j, 0.+0.j, 0.+0.j, 0.+0.j, 0.+0.j, 0.+0.j, 0.+0.j, 0.+0.j,
 0.+0.j, 0.+0.j, 0.+0.j, 0.+0.j, 0.+0.j, 0.+0.j, 0.+0.j, 0.+0.j]

Very simply we have data in bin 0 (ones) and nothing in any other bin (the rest is zeros)

I have then taken two copies of the intel FFT core as configured in the post above; and I have set the "inverse" port of one of the instances to 0 and in the other instance it is set to 1. So I am expecting that one of the instances will calculate the FFT and one will calculate the IFFT.

For reference the FFT of this input array is:

[16.+16.j,  0. +0.j,  0. +0.j,  0. +0.j,  0. +0.j,  0. +0.j,
 0. +0.j,  0. +0.j,  0. +0.j,  0. +0.j,  0. +0.j,  0. +0.j,
 0. +0.j,  0. +0.j,  0. +0.j,  0. +0.j]

When I then run a simulation of the two cores I get the following outputs

Instance 1 - "inverse" driven to 0

(16.000000 16.000000)
(0.000000 0.000000)
(0.000000 0.000000)
(0.000000 0.000000)
(0.000000 0.000000)
(0.000000 0.000000)
(0.000000 0.000000)
(0.000000 0.000000)
(0.000000 0.000000)
(0.000000 0.000000)
(0.000000 0.000000)
(0.000000 0.000000)
(0.000000 0.000000)
(0.000000 0.000000)
(0.000000 0.000000)
(0.000000 0.000000)

Instance 2 - "inverse" driven to 1

(16.000000 16.000000) 
(0.000000 0.000000)
(0.000000 0.000000)
(0.000000 0.000000)
(0.000000 0.000000)
(0.000000 0.000000)
(0.000000 0.000000)
(0.000000 0.000000)
(0.000000 0.000000)
(0.000000 0.000000)
(0.000000 0.000000)
(0.000000 0.000000)
(0.000000 0.000000)
(0.000000 0.000000)
(0.000000 0.000000)
(0.000000 0.000000)

(Please note that if we express these values in exponent form "%e" we actually see that some of the "zero" values are actually very very small decimal values that are just greater than 0, but I can accept some variation from the expected values).

However the Big Problem here is that no matter whether I drive the "inverse" port to 1 or 0, I am only getting the forward FFT and it never calculates an IFFT for me.

For clarity, the "inverse" port value is hard coded and a reset event happens at the beginning of the simulation for 5 clock cycles before data is sent to the core.

Does anyone have any ideas on what I might be doing wrong to configure the core to give me IFFTs?

Thanks!