Create a FEE Transmission End flag for the SW

[rodmarfran]

Issue:

• A FEE Transmission End flag needs to be added, so the SW can know when the transmission is completed, allowing it to correct the program flow without delay.

Fix:

• Add a NIOS II accessible register for this configuration;
• Create a FEE Transmission End flag in HW;
• Create the necessary APIs and Defines to change this in SW.

[rodmarfran]

It was decided to use a FEE Machine busy flag for this control, to avoid having to clear a trigger flag of Transmission End. If the FEE Machine is not busy, the transmission of the Data Packets is finished.

A busy flag to indicate if the FEE Machine is working was added in commit 388d766.

Change Log:

• Two extra bits (fee_right_machine_busy and fee_left_machine_busy) were added to the fee_windowing_buffers_status register.
• The necessary logic was created to indicate when the FEE Machine is busy (FEE Machine not busy indicate the end of a transmission).

Remaining Fixes:

• Modify the necessary APIs and Defines to change this in SW.

[rodmarfran]

The necessary APIs and Defines were changed in the SW, in commit 5fa17b7.

Change Log:

• Defines to access the new flags were added into "comm.h" file.
• The bFeebGetBuffersStatus function wasmodified to support these flags.
• bFeebGetCh1LeftFeeBusy, bFeebGetCh1RightFeeBusy, bFeebGetCh2LeftFeeBusy and bFeebGetCh2RightFeeBusy functions were created to support these flags.

Remaining:

• Test the modified APIs and HW.

[rodmarfran]

The busy flag implementation was synthesized and tested in HW 14, in commit 05a8fbd.
A bug was discovered in the current implementation, because the busy flag is getting cleared when the fee-machine finishes writing data to the send buffer, but not when the send buffer finished transmitting the data over the SpaceWire link.

Change Log:

Remaining:

• Correct the busy flag bug.

[rodmarfran]

The busy flag wrong behavior was corrected and simulated, in commit 337c495, and synthesized for tests in HW V18, in commit 71cd1ad.
Now the busy flag only clears when all the data was transfered from the send buffer to the SpaceWire codec, when it's safe for the SW to issue a "stop" command to the HW fee-machine.

Change Log:

• Two new wait states were added to the FEE Machine, to ensure that all of the data was transfered from the send buffer before it goes to an idle state.

Remaining:

• @ericolucasm to test the HW V18 to check if the busy flag behavior improved. If it works properly, the SW guard time after the transmission end can be reduced to 0 without packages being lost in the transmission.

Test Procedure:

• Check if all the 638 read-out cycle packages are still being transmitted with a large guard time (50 ms) [a bug was created if it does not work];
• Then, check if all the 638 read-out cycle packages are still being transmitted with a small guard time (1 ms) [good behavior of the busy flag];
• Last, check if all the 638 read-out cycle packages are still being transmitted with a no guard time (0 ms) [best behavior of the busy flag. The issue can be closed if this works];

Hardware Programming File:

• SimuCam_V18_20190222_HW.sof: https://github.com/NSEE/SimuCam_Development/blob/71cd1ad27242a16b499cd3cbf2e2ed4126f370e5/G3U_HW_V02_2GB/Quartus_Project/output_files/SimuCam_V18_20190222_HW.sof