tchisholmuk
Newbie level 4
Hi,
I am using Design Compiler to insert a scan chain in a design, but when simulating after insertion the Scan Data Out is inverted with respect to Scan Data In.
I can see the scan data being inverted at several points throughout the scan path, however it always ends up being inverted for the output.
The commands I am using for scan insertion is below. I have tried the same steps on a different design and the scan path is correct.
I have tried:
I can't find anything in the DFT Compiler user guide relating to this other than the items above. It does say it will choose to take Q or QN as a scan data output depending on fanout, but not why the final output might be inverted.
Any help would be greatly appreciated.
Tom
I am using Design Compiler to insert a scan chain in a design, but when simulating after insertion the Scan Data Out is inverted with respect to Scan Data In.
I can see the scan data being inverted at several points throughout the scan path, however it always ends up being inverted for the output.
The commands I am using for scan insertion is below. I have tried the same steps on a different design and the scan path is correct.
I have tried:
- Using the hookup_sense option in set_dft_signal (no effect either way)
- Setting test_disable_find_best_scan_out (true and false)
- Performing the same steps with another design (works correctly)
I can't find anything in the DFT Compiler user guide relating to this other than the items above. It does say it will choose to take Q or QN as a scan data output depending on fanout, but not why the final output might be inverted.
Any help would be greatly appreciated.
Tom
Code:
set_dft_drc_configuration -internal_pins enable
set_dft_signal -view existing_dft -type ScanClock -hookup_pin PAD_Clock/C -timing {5 15}
set_dft_signal -view existing_dft -type Reset -hookup_pin SYNC_DFC1_2/Q -active_state 0
set_dft_signal -view spec -type ScanEnable -hookup_pin PAD_Test/C -port Test -active_state 1
set_dft_signal -view existing_dft -type TestMode -hookup_pin PAD_Test/C -port Test -active_state 1
set_dft_signal -view spec -type ScanDataIn -hookup_pin PAD_SDI/C -port SDI
set_dft_signal -view spec -type ScanDataOut -hookup_pin PAD_SDO/I -port SDO
create_test_protocol
dft_drc
set_scan_configuration -chain_count 1
preview_dft
insert_dft
dft_drc